Add Prometheus metrics integration (v0.7.4)

- New Metrics settings tab with enable/disable toggle
- PrometheusController for wp_prometheus_collect_metrics hook
- License gauges: total by status, lifetime, expiring, expiring soon
- Download gauges: total downloads, active versions
- API counters: requests, rate limits, validation errors
- Metric tracking in RestApiController and UpdateController

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitea/workflows/release.yml

@@ -0,0 +1,228 @@
+name: Create Release Package
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  build-release:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.3'
+          extensions: mbstring, xml, zip, intl, gettext
+          tools: composer:v2
+
+      - name: Get version from tag
+        id: version
+        run: |
+          VERSION=${GITHUB_REF_NAME#v}
+          echo "version=$VERSION" >> $GITHUB_OUTPUT
+          echo "Building version: $VERSION"
+
+      - name: Validate composer.json
+        run: composer validate --no-check-lock --no-check-all
+
+      - name: Install Composer dependencies (production)
+        run: |
+          composer config platform.php 8.3.0
+          composer install --no-dev --optimize-autoloader --no-interaction
+
+      - name: Fix vendor symlink
+        run: |
+          # If client is a symlink, replace with actual files
+          if [ -L "vendor/magdev/wc-licensed-product-client" ]; then
+            echo "Found symlink, replacing with actual files..."
+            TARGET=$(readlink -f vendor/magdev/wc-licensed-product-client)
+            rm vendor/magdev/wc-licensed-product-client
+            cp -r "$TARGET" vendor/magdev/wc-licensed-product-client
+          fi
+          ls -la vendor/magdev/
+
+      - name: Install gettext
+        run: apt-get update && apt-get install -y gettext
+
+      - name: Compile translations
+        run: |
+          for po in languages/*.po; do
+            if [ -f "$po" ]; then
+              mo="${po%.po}.mo"
+              echo "Compiling $po to $mo"
+              msgfmt -o "$mo" "$po"
+            fi
+          done
+
+      - name: Verify plugin version matches tag
+        run: |
+          PLUGIN_VERSION=$(grep -oP "Version:\s*\K[0-9]+\.[0-9]+\.[0-9]+" wc-licensed-product.php | head -1)
+          TAG_VERSION=${{ steps.version.outputs.version }}
+          if [ "$PLUGIN_VERSION" != "$TAG_VERSION" ]; then
+            echo "Error: Plugin version ($PLUGIN_VERSION) does not match tag version ($TAG_VERSION)"
+            exit 1
+          fi
+          echo "Version verified: $PLUGIN_VERSION"
+
+      - name: Create release directory
+        run: mkdir -p releases
+
+      - name: Build release package
+        run: |
+          VERSION=${{ steps.version.outputs.version }}
+          PLUGIN_NAME="wc-licensed-product"
+          RELEASE_FILE="releases/${PLUGIN_NAME}-${VERSION}.zip"
+
+          cd ..
+          zip -r "${PLUGIN_NAME}/${RELEASE_FILE}" "${PLUGIN_NAME}" \
+            -x "${PLUGIN_NAME}/.git/*" \
+            -x "${PLUGIN_NAME}/.gitea/*" \
+            -x "${PLUGIN_NAME}/.github/*" \
+            -x "${PLUGIN_NAME}/.vscode/*" \
+            -x "${PLUGIN_NAME}/.claude/*" \
+            -x "${PLUGIN_NAME}/CLAUDE.md" \
+            -x "${PLUGIN_NAME}/wp-core" \
+            -x "${PLUGIN_NAME}/wp-core/*" \
+            -x "${PLUGIN_NAME}/wp-plugins" \
+            -x "${PLUGIN_NAME}/wp-plugins/*" \
+            -x "${PLUGIN_NAME}/releases/*" \
+            -x "${PLUGIN_NAME}/composer.lock" \
+            -x "${PLUGIN_NAME}/*.log" \
+            -x "${PLUGIN_NAME}/.gitignore" \
+            -x "${PLUGIN_NAME}/.gitmodules" \
+            -x "${PLUGIN_NAME}/.editorconfig" \
+            -x "${PLUGIN_NAME}/phpcs.xml*" \
+            -x "${PLUGIN_NAME}/phpunit.xml*" \
+            -x "${PLUGIN_NAME}/tests/*" \
+            -x "${PLUGIN_NAME}/*.po~" \
+            -x "${PLUGIN_NAME}/*.bak" \
+            -x "${PLUGIN_NAME}/lib/*" \
+            -x "${PLUGIN_NAME}/lib/*/.git/*" \
+            -x "${PLUGIN_NAME}/vendor/magdev/*/.git/*" \
+            -x "${PLUGIN_NAME}/vendor/magdev/*/CLAUDE.md" \
+            -x "*.DS_Store"
+
+          cd "${PLUGIN_NAME}"
+          echo "Created: ${RELEASE_FILE}"
+          ls -lh "${RELEASE_FILE}"
+
+      - name: Generate checksums
+        run: |
+          VERSION=${{ steps.version.outputs.version }}
+          PLUGIN_NAME="wc-licensed-product"
+
+          cd releases
+          sha256sum "${PLUGIN_NAME}-${VERSION}.zip" > "${PLUGIN_NAME}-${VERSION}.zip.sha256"
+          echo "SHA256:"
+          cat "${PLUGIN_NAME}-${VERSION}.zip.sha256"
+
+      - name: Verify package structure
+        run: |
+          set +o pipefail
+          VERSION=${{ steps.version.outputs.version }}
+          PLUGIN_NAME="wc-licensed-product"
+
+          echo "Package contents (first 50 entries):"
+          unzip -l "releases/${PLUGIN_NAME}-${VERSION}.zip" | head -50 || true
+
+          # Verify main plugin file exists
+          if unzip -l "releases/${PLUGIN_NAME}-${VERSION}.zip" | grep -q "${PLUGIN_NAME}/${PLUGIN_NAME}.php"; then
+            echo "Main plugin file: OK"
+          else
+            echo "ERROR: Main plugin file not found!"
+            exit 1
+          fi
+
+          # Verify vendor directory included
+          if unzip -l "releases/${PLUGIN_NAME}-${VERSION}.zip" | grep -q "${PLUGIN_NAME}/vendor/"; then
+            echo "Vendor directory: OK"
+          else
+            echo "ERROR: Vendor directory not found!"
+            exit 1
+          fi
+
+          # Verify lib directory excluded
+          if unzip -l "releases/${PLUGIN_NAME}-${VERSION}.zip" | grep -q "${PLUGIN_NAME}/lib/"; then
+            echo "WARNING: lib/ directory should be excluded"
+          else
+            echo "lib/ excluded: OK"
+          fi
+
+      - name: Extract changelog for release notes
+        id: changelog
+        run: |
+          VERSION=${{ steps.version.outputs.version }}
+          NOTES=$(sed -n "/^## \[${VERSION}\]/,/^## \[/p" CHANGELOG.md | sed '$ d' | tail -n +2)
+          if [ -z "$NOTES" ]; then
+            NOTES="Release version ${VERSION}"
+          fi
+          echo "$NOTES" > release_notes.txt
+          echo "Release notes extracted"
+
+      - name: Create Gitea Release
+        env:
+          GITEA_TOKEN: ${{ secrets.SRC_GITEA_TOKEN }}
+        run: |
+          VERSION=${{ steps.version.outputs.version }}
+          TAG_NAME=${{ github.ref_name }}
+          PLUGIN_NAME="wc-licensed-product"
+
+          PRERELEASE="false"
+          if [[ "$TAG_NAME" == *-* ]]; then
+            PRERELEASE="true"
+          fi
+
+          BODY=$(cat release_notes.txt)
+
+          # Check if release already exists and delete it
+          EXISTING_RELEASE=$(curl -s \
+            -H "Authorization: token ${GITEA_TOKEN}" \
+            "${GITHUB_SERVER_URL}/api/v1/repos/${GITHUB_REPOSITORY}/releases/tags/${TAG_NAME}")
+
+          EXISTING_ID=$(echo "$EXISTING_RELEASE" | jq -r '.id // empty')
+          if [ -n "$EXISTING_ID" ] && [ "$EXISTING_ID" != "null" ]; then
+            echo "Deleting existing release ID: $EXISTING_ID"
+            curl -s -X DELETE \
+              -H "Authorization: token ${GITEA_TOKEN}" \
+              "${GITHUB_SERVER_URL}/api/v1/repos/${GITHUB_REPOSITORY}/releases/${EXISTING_ID}"
+            echo "Existing release deleted"
+          fi
+
+          # Create release via Gitea API
+          RELEASE_RESPONSE=$(curl -s -X POST \
+            -H "Authorization: token ${GITEA_TOKEN}" \
+            -H "Content-Type: application/json" \
+            -d "{\"tag_name\": \"${TAG_NAME}\", \"name\": \"Release ${VERSION}\", \"body\": $(echo "$BODY" | jq -Rs .), \"draft\": false, \"prerelease\": ${PRERELEASE}}" \
+            "${GITHUB_SERVER_URL}/api/v1/repos/${GITHUB_REPOSITORY}/releases")
+
+          RELEASE_ID=$(echo "$RELEASE_RESPONSE" | jq -r '.id')
+
+          if [ "$RELEASE_ID" == "null" ] || [ -z "$RELEASE_ID" ]; then
+            echo "Failed to create release:"
+            echo "$RELEASE_RESPONSE"
+            exit 1
+          fi
+
+          echo "Created release ID: $RELEASE_ID"
+
+          # Upload release assets
+          for file in "releases/${PLUGIN_NAME}-${VERSION}.zip" "releases/${PLUGIN_NAME}-${VERSION}.zip.sha256"; do
+            if [ -f "$file" ]; then
+              FILENAME=$(basename "$file")
+              echo "Uploading $FILENAME..."
+              curl -s -X POST \
+                -H "Authorization: token ${GITEA_TOKEN}" \
+                -H "Content-Type: application/octet-stream" \
+                --data-binary "@$file" \
+                "${GITHUB_SERVER_URL}/api/v1/repos/${GITHUB_REPOSITORY}/releases/${RELEASE_ID}/assets?name=${FILENAME}"
+              echo "Uploaded $FILENAME"
+            fi
+          done
+
+          echo "Release created: ${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/releases/tag/${TAG_NAME}"

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "lib/wc-licensed-product-client"]
+	path = lib/wc-licensed-product-client
+	url = ../wc-licensed-product-client.git

CHANGELOG.md

@@ -7,6 +7,91 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.7.4] - 2026-02-03
+
+### Added
+
+- **Prometheus Metrics Integration**: Expose license and API metrics for monitoring
+  - New "Metrics" settings tab with enable/disable toggle
+  - License gauges: total by status, lifetime, expiring, expiring soon
+  - Download gauges: total downloads, active versions count
+  - API counters: requests by endpoint/result, rate limit exceeded events, validation errors by type
+  - Requires [WP Prometheus](https://src.bundespruefstelle.ch/magdev/wp-prometheus) plugin
+
+### New Files
+
+- `src/Metrics/PrometheusController.php` - Prometheus metrics collection and registration
+
+### Technical Details
+
+- Hooks into `wp_prometheus_collect_metrics` action for metric collection
+- API counters stored persistently in WordPress options (`wclp_prometheus_counters`)
+- Static methods for incrementing counters from API controllers
+- Metrics only collected when enabled in settings
+
+## [0.7.3] - 2026-02-01
+
+### Fixed
+
+- **Docker Environment Support:** API Verification Secret now visible on customer licenses page in Docker environments
+  - Added `ResponseSigner::getServerSecret()` method to check multiple sources for server secret
+  - Checks PHP constant, `getenv()`, `$_ENV`, and `$_SERVER` in priority order
+  - Maintains full backward compatibility with standard WordPress installations
+
+### Changed
+
+- Updated `Plugin.php` to use `ResponseSigner::isSigningEnabled()` instead of direct constant check
+
+### Technical Details
+
+- Root cause: Docker WordPress setups using `wp-config-docker.php` with `getenv_docker()` don't always define PHP constants
+- The environment variable was accessible but the constant wasn't being created
+- New `getServerSecret()` method centralizes all server secret retrieval logic
+
+## [0.7.2] - 2026-01-29
+
+### Added
+
+- **Gitea CI/CD Pipeline**: Automated release workflow triggered on version tags
+  - Automatic package creation with proper WordPress subdirectory structure
+  - SHA256 checksum generation for package integrity
+  - Changelog extraction for release notes
+  - Pre-release detection for hyphenated tags (e.g., `v0.7.2-rc1`)
+
+### Changed
+
+- **Git Submodule Migration**: `magdev/wc-licensed-product-client` is now a git submodule
+  - Located at `lib/wc-licensed-product-client` instead of being fetched via Composer VCS
+  - Composer now uses `path` type repository pointing to local submodule
+  - Improves version control clarity and development workflow
+  - Symlinked to `vendor/` during `composer install`
+
+### Developer Notes
+
+- New file: `.gitea/workflows/release.yml` for CI/CD automation
+- Updated `composer.json`: Repository type changed from `vcs` to `path`
+- Created `.gitmodules` for submodule tracking
+- Release packages now exclude `lib/` directory (vendor has installed copy)
+- Submodule checkout required: `git submodule update --init --recursive`
+
+## [0.7.1] - 2026-01-28
+
+### Fixed
+
+- **CRITICAL:** Fixed API Verification Secret not displayed in PHP fallback template on customer account licenses page
+- Response signing now includes `/update-check` endpoint (was missing from signed routes)
+
+### Changed
+
+- Updated `magdev/wc-licensed-product-client` dependency to v0.2.2
+- Updated `symfony/http-client` dependency to v7.4.5
+
+### Technical Details
+
+- Added customer secret display to `displayLicensesFallback()` method in `AccountController`
+- Added `/update-check` route to `ResponseSigner::shouldSign()` method for consistent signature headers
+- Verified server implementation aligns with updated client library documentation
+
 ## [0.7.0] - 2026-01-28
 
 ### Security

CLAUDE.md

@@ -32,14 +32,9 @@ This project is proudly **"vibe-coded"** using Claude.AI - the entire codebase w
 
 **Note for AI Assistants:** Clean this section after the specific features are done or new releases are made. Effective changes are tracked in `CHANGELOG.md`. Do not add completed versions here - document them in the Session History section at the end of this file.
 
-### Version 0.7.0
+### Known Bugs
 
-This is a security version. It includes a full security audit and a remote check of a live version of this plugin on <https://shop.magdev.cc>. The shop is the property of the plugin developer, all actions are permitted.
+None currently tracked.
-
-- Check the sourcecode for best practises of all involved components, including checks for SQLi, XSRF, XSS and similar techniques
-- Check the remote version for the OWASP Top 10
-- Check the whole licensing workflow
-- Minimize the thread vectors
 
 ## Technical Stack
 
@@ -60,6 +55,13 @@ This is a security version. It includes a full security audit and a remote check
 - Nonce verification on form submissions
 - Output escaping in templates (`esc_attr`, `esc_html`, `esc_js`)
 - Direct file access prevention via `ABSPATH` check
+- XSS-safe DOM construction in JavaScript (no `innerHTML` with user data)
+- Rate limiting on API endpoints (configurable via `WC_LICENSE_RATE_LIMIT`)
+- Rate limiting on frontend operations (transfers: 5/hour, downloads: 30/hour)
+- CSV import limits (2MB max, 1000 rows max, 5-minute cooldown)
+- IP detection with proxy support via `IpDetectionTrait` (supports `WC_LICENSE_TRUSTED_PROXIES`)
+- SQL injection prevention using `$wpdb->prepare()` throughout
+- Secure download URLs with hash verification using `hash_equals()`
 
 ### Translation Ready
 
@@ -1843,3 +1845,148 @@ Security-focused release with comprehensive audit and hardening. Performed OWASP
 - Created release package: `releases/wc-licensed-product-0.7.0.zip` (883 KB)
 - SHA256: `12f8452316e350273003f36bf6d7b7121a7bedc9a6964c3d0732d26318d94c18`
 - Tagged as `v0.7.0` and pushed to `main` branch
+
+### 2026-01-28 - Version 0.7.1 - Bug Fixes & Client Compatibility
+
+**Overview:**
+
+Bug fix release ensuring compatibility with updated `magdev/wc-licensed-product-client` v0.2.2 and fixing API Verification Secret display.
+
+**Bug Fixes:**
+
+- **CRITICAL:** Fixed API Verification Secret not displaying on customer account licenses page when using PHP fallback (Twig unavailable)
+- Fixed `/update-check` endpoint responses not being signed (missing from `ResponseSigner::shouldSign()`)
+
+**Dependency Updates:**
+
+- Updated `magdev/wc-licensed-product-client` from `760e1e7` to `56abe8a` (v0.2.2)
+- Updated `symfony/http-client` from v7.4.4 to v7.4.5
+
+**Modified files:**
+
+- `src/Frontend/AccountController.php` - Added customer secret display to PHP fallback method `displayLicensesFallback()`
+- `src/Api/ResponseSigner.php` - Added `/update-check` to `shouldSign()` method
+
+**Technical notes:**
+
+- PHP fallback template now includes the collapsible API Verification Secret section matching the Twig template
+- All four API endpoints (`/validate`, `/status`, `/activate`, `/update-check`) now include signature headers when `WC_LICENSE_SERVER_SECRET` is configured
+- Client library v0.2.2 verified compatible with server implementation
+
+**Release v0.7.1:**
+
+- Created release package: `releases/wc-licensed-product-0.7.1.zip` (886 KB)
+- SHA256: `6ffd0bdf47395436bbc28a029eff4c6d065f2b5b64c687b96ae36a74c3ee34ef`
+- Tagged as `v0.7.1` and pushed to `main` branch
+
+### 2026-01-29 - Version 0.7.2 - Git Submodule & CI/CD Pipeline
+
+**Overview:**
+
+Infrastructure release converting the client library dependency to a git submodule and implementing automated CI/CD releases via Gitea Actions.
+
+**Git Submodule Migration:**
+
+- Converted `magdev/wc-licensed-product-client` from Composer VCS dependency to git submodule
+- Submodule located at `lib/wc-licensed-product-client`
+- Composer uses `path` type repository pointing to local submodule
+- Symlinked to `vendor/magdev/wc-licensed-product-client` during `composer install`
+
+**Gitea CI/CD Pipeline:**
+
+- New workflow at `.gitea/workflows/release.yml`
+- Triggers on version tags (`v*`)
+- Automated steps:
+  - Checkout with recursive submodules
+  - PHP 8.3 setup with required extensions
+  - Composer dependency installation (production only)
+  - Translation compilation (`.po` to `.mo`)
+  - Version verification against plugin header
+  - Release package creation with proper exclusions
+  - SHA256 checksum generation
+  - Package structure verification
+  - Changelog extraction for release notes
+  - Gitea release creation with asset upload
+  - Pre-release detection for hyphenated tags
+
+**New files:**
+
+- `.gitea/workflows/release.yml` - Gitea Actions workflow for automated releases
+- `.gitmodules` - Git submodule configuration (created by git)
+
+**Modified files:**
+
+- `composer.json` - Changed repository type from `vcs` to `path`, URL to `lib/wc-licensed-product-client`
+- `CHANGELOG.md` - Added v0.7.2 release notes
+- `CLAUDE.md` - Removed v0.7.2 from roadmap, added session history
+
+**Package Exclusions:**
+
+Release packages exclude: `.git/`, `.gitea/`, `.gitmodules`, `lib/` (submodule source), `vendor/**/.git`, `tests/`, `CLAUDE.md`, `*.po~`, `wp-core`, `wp-plugins`, `composer.lock`
+
+**Developer Workflow Changes:**
+
+After cloning the repository, developers must now run:
+
+```bash
+git submodule update --init --recursive
+composer install
+```
+
+**Technical notes:**
+
+- Path repository uses `*` version constraint with `symlink: false` option
+- CI replaces symlink with actual files via `cp -r` before packaging
+- CI uses `actions/checkout@v4` with `submodules: recursive` for proper submodule initialization
+- Release creation uses direct Gitea API calls (`/api/v1/repos/.../releases`)
+- Requires `SRC_GITEA_TOKEN` secret configured in Gitea repository settings
+- Workflow completed successfully: 57 seconds, all checks passed
+
+**Release v0.7.2:**
+
+- Automatically created by Gitea Actions CI/CD pipeline
+- Release package: 881 KiB with SHA256 checksum
+- First automated release - all future releases will use this workflow
+
+**Additional fixes (same session):**
+
+- Updated README.md with Auto-Updates section and Development section
+- Fixed CI/CD workflow to handle existing releases (delete before recreate)
+- When updating a tag, the workflow now checks for existing releases and deletes them first
+
+**Lessons learned:**
+
+- Gitea releases persist even when their tag is deleted - must delete release via API
+- Composer `symlink: false` doesn't always work - CI must manually replace symlinks with `cp -r`
+- Never create zip archives locally on this machine (fills up RAM indefinitely)
+- Gitea API endpoint for releases by tag: `GET /api/v1/repos/{owner}/{repo}/releases/tags/{tag}`
+
+### 2026-02-01 - Bug Fix: API Verification Secret Not Visible
+
+**Overview:**
+
+Fixed the "API Verification Secret" (customer secret) not appearing on the customer account licenses page in Docker environments.
+
+**Root Cause:**
+
+The `WC_LICENSE_SERVER_SECRET` constant was not being defined even though the environment variable was set. In Docker WordPress setups using `wp-config-docker.php`, the `getenv_docker()` function retrieves values from environment variables, but the constant wasn't being created properly. The plugin was only checking for the PHP constant, not the environment variable directly.
+
+**Fix:**
+
+Added `ResponseSigner::getServerSecret()` static method that checks multiple sources for the server secret:
+
+1. `WC_LICENSE_SERVER_SECRET` constant (standard WordPress configuration)
+2. `getenv('WC_LICENSE_SERVER_SECRET')` (Docker environments)
+3. `$_ENV['WC_LICENSE_SERVER_SECRET']` (some PHP configurations)
+4. `$_SERVER['WC_LICENSE_SERVER_SECRET']` (fallback)
+
+**Modified files:**
+
+- `src/Api/ResponseSigner.php` - Added `getServerSecret()` method, updated `isSigningEnabled()` and `getCustomerSecretForLicense()` to use it
+- `src/Plugin.php` - Updated to use `ResponseSigner::isSigningEnabled()` instead of direct constant check
+
+**Technical notes:**
+
+- The fix maintains backward compatibility with standard WordPress installations using constants
+- Docker environments can now use environment variables directly without needing the constant to be defined
+- All three methods (`isSigningEnabled()`, `getCustomerSecretForLicense()`, and constructor) now use the centralized `getServerSecret()` method

README.md

@@ -21,9 +21,12 @@ WC Licensed Product adds a new product type "Licensed Product" to WooCommerce, e
 - **Version Binding**: Optional binding to major software versions
 - **Expiration Support**: Set license validity periods or lifetime licenses
 - **Rate Limiting**: API endpoints protected with configurable rate limiting (default: 30 requests/minute)
+- **Frontend Rate Limiting**: Transfer requests (5/hour) and downloads (30/hour) protected against abuse
 - **Trusted Proxy Support**: Configurable trusted proxies for accurate rate limiting behind CDNs
 - **Checkout Blocks**: Full support for WooCommerce Checkout Blocks (default since WC 8.3+)
 - **Self-Licensing**: The plugin can validate its own license (for commercial distribution)
+- **WordPress Auto-Updates**: Receive plugin updates through WordPress's native update system
+- **Automated Releases**: CI/CD pipeline for consistent release packaging
 
 ### Customer Features
 
@@ -132,17 +135,26 @@ When a customer purchases a licensed product, they must enter the domain where t
 3. Upload a CSV file (supports exported format or simplified format)
 4. Choose options: skip header row, update existing licenses
 
+**Import Limits (Security):**
+
+- Maximum file size: 2MB
+- Maximum rows per import: 1000
+- Cooldown between imports: 5 minutes
+
 ## Security
 
 The plugin implements several security best practices:
 
 - **Input Sanitization**: All user inputs are sanitized using WordPress functions
 - **Output Escaping**: All output is escaped to prevent XSS attacks
+- **XSS-Safe DOM Construction**: JavaScript uses `createElement()` and `textContent` instead of `innerHTML`
 - **CSRF Protection**: Nonce verification on all forms and AJAX requests
 - **SQL Injection Prevention**: All database queries use prepared statements
 - **Capability Checks**: Admin functions require `manage_woocommerce` capability
 - **Secure Downloads**: File downloads use hash-verified URLs with user authentication
 - **Response Signing**: Optional HMAC-SHA256 signatures for API tamper protection
+- **Rate Limiting**: API and frontend operations protected against abuse
+- **Import Limits**: CSV imports limited by file size, row count, and cooldown period
 
 ### Trusted Proxy Configuration
 
@@ -330,6 +342,41 @@ Content-Type: application/json
 | `max_activations_reached` | Maximum activations reached |
 | `rate_limit_exceeded` | Too many requests (wait and retry) |
 
+## Auto-Updates
+
+Licensed plugins can receive updates through WordPress's native plugin update system. When properly configured, WordPress will check the license server for updates and display them in the Plugins page.
+
+### Configuration
+
+In WooCommerce > Settings > Licensed Products > Auto-Updates:
+
+- **Enable Update Notifications**: Show available updates in WordPress admin
+- **Automatically Install Updates**: Let WordPress install updates automatically
+- **Update Check Frequency**: How often to check for updates (1-168 hours)
+
+### How It Works
+
+1. The plugin periodically checks the configured license server for updates
+2. If a newer version is available and the license is valid, WordPress shows the update
+3. Updates can be installed manually or automatically (if enabled)
+4. Downloads are authenticated using the license key
+
+### API Endpoint
+
+The update check uses the `/update-check` REST API endpoint:
+
+```http
+POST /wp-json/wc-licensed-product/v1/update-check
+Content-Type: application/json
+
+{
+  "license_key": "XXXX-XXXX-XXXX-XXXX",
+  "domain": "example.com",
+  "plugin_slug": "my-plugin",
+  "current_version": "1.0.0"
+}
+```
+
 ## License Statuses
 
 - **Active**: License is valid and usable
@@ -359,6 +406,60 @@ For issues and feature requests, please visit:
 
 Marco Graetsch
 
+## Development
+
+### Setup
+
+After cloning the repository, initialize the git submodule and install dependencies:
+
+```bash
+git clone https://src.bundespruefstelle.ch/magdev/wc-licensed-product.git
+cd wc-licensed-product
+git submodule update --init --recursive
+composer install
+```
+
+### Project Structure
+
+- `src/` - PHP source files (PSR-4 autoloaded)
+- `assets/` - CSS and JavaScript files
+- `templates/` - Twig templates for admin and frontend views
+- `languages/` - Translation files (.pot, .po, .mo)
+- `lib/` - Git submodule for the client library
+- `docs/` - API documentation and client examples
+
+### Creating Releases
+
+Releases are automatically created by the Gitea CI/CD pipeline when a version tag is pushed:
+
+```bash
+# Update version in wc-licensed-product.php (both header and constant)
+# Update CHANGELOG.md with release notes
+git add -A && git commit -m "Release v0.7.3"
+git tag -a v0.7.3 -m "Release v0.7.3"
+git push origin main --tags
+```
+
+The pipeline will:
+
+1. Build production dependencies
+2. Compile translations
+3. Create the release package with proper WordPress structure
+4. Generate SHA256 checksum
+5. Publish to Gitea releases
+
+### Translations
+
+To add or update translations:
+
+```bash
+# Extract strings to .pot template
+# (Use a tool like wp-cli or poedit)
+
+# Compile .po files to .mo for production
+for po in languages/*.po; do msgfmt -o "${po%.po}.mo" "$po"; done
+```
+
 ## License
 
 GPL-2.0-or-later

composer.json

@@ -12,14 +12,17 @@
     ],
     "repositories": [
         {
-            "type": "vcs",
+            "type": "path",
-            "url": "https://src.bundespruefstelle.ch/magdev/wc-licensed-product-client.git"
+            "url": "lib/wc-licensed-product-client",
+            "options": {
+                "symlink": false
+            }
         }
     ],
     "require": {
         "php": ">=8.3.0",
         "twig/twig": "^3.0",
-        "magdev/wc-licensed-product-client": "dev-main"
+        "magdev/wc-licensed-product-client": "*"
     },
     "autoload": {
         "psr-4": {

composer.lock

@@ -4,15 +4,15 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "05af8ab515abe7e689c610724b54e27a",
+    "content-hash": "f13b7ed9531068d0180f28adc8a80397",
     "packages": [
         {
             "name": "magdev/wc-licensed-product-client",
             "version": "dev-main",
-            "source": {
+            "dist": {
-                "type": "git",
+                "type": "path",
-                "url": "https://src.bundespruefstelle.ch/magdev/wc-licensed-product-client.git",
+                "url": "lib/wc-licensed-product-client",
-                "reference": "760e1e752a0c088fa634cf7ff678e0735ed525a4"
+                "reference": "f9281ec5fb23bf1993ab0240e0347c835009a10f"
             },
             "require": {
                 "php": "^8.3",
@@ -24,7 +24,6 @@
             "require-dev": {
                 "phpunit/phpunit": "^11.0"
             },
-            "default-branch": true,
             "type": "library",
             "autoload": {
                 "psr-4": {
@@ -52,7 +51,9 @@
                 "issues": "https://src.bundespruefstelle.ch/magdev/wc-licensed-product-client/issues",
                 "source": "https://src.bundespruefstelle.ch/magdev/wc-licensed-product-client"
             },
-            "time": "2026-01-27T19:52:12+00:00"
+            "transport-options": {
+                "relative": true
+            }
         },
         {
             "name": "psr/cache",
@@ -380,16 +381,16 @@
         },
         {
             "name": "symfony/http-client",
-            "version": "v7.4.4",
+            "version": "v7.4.5",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/http-client.git",
-                "reference": "d63c23357d74715a589454c141c843f0172bec6c"
+                "reference": "84bb634857a893cc146cceb467e31b3f02c5fe9f"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/http-client/zipball/d63c23357d74715a589454c141c843f0172bec6c",
+                "url": "https://api.github.com/repos/symfony/http-client/zipball/84bb634857a893cc146cceb467e31b3f02c5fe9f",
-                "reference": "d63c23357d74715a589454c141c843f0172bec6c",
+                "reference": "84bb634857a893cc146cceb467e31b3f02c5fe9f",
                 "shasum": ""
             },
             "require": {
@@ -457,7 +458,7 @@
                 "http"
             ],
             "support": {
-                "source": "https://github.com/symfony/http-client/tree/v7.4.4"
+                "source": "https://github.com/symfony/http-client/tree/v7.4.5"
             },
             "funding": [
                 {
@@ -477,7 +478,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2026-01-23T16:34:22+00:00"
+            "time": "2026-01-27T16:16:02+00:00"
         },
         {
             "name": "symfony/http-client-contracts",

docs/server-implementation.md

@@ -21,7 +21,7 @@ This prevents attackers from:
 
 ## Requirements
 
-- PHP 7.4+ (8.0+ recommended)
+- PHP 8.3+
 - A server secret stored securely (not in version control)
 
 ## Server Configuration
@@ -51,25 +51,33 @@ php -r "echo bin2hex(random_bytes(32));"
 
 ### Key Derivation
 
-Each license key gets a unique signing key derived from the server secret:
+Each license key gets a unique signing key derived from the server secret using RFC 5869 HKDF:
 
 ```php
 /**
  * Derive a unique signing key for a license.
  *
- * @param string $licenseKey The license key
+ * Uses PHP's native hash_hkdf() function per RFC 5869.
- * @param string $serverSecret The server's master secret
+ *
- * @return string The derived key (hex encoded)
+ * @param string $licenseKey The license key (used as "info" context)
+ * @param string $serverSecret The server's master secret (used as IKM)
+ * @return string The derived key (hex encoded, 64 characters)
  */
 function derive_signing_key(string $licenseKey, string $serverSecret): string
 {
-    // HKDF-like key derivation
+    // HKDF key derivation per RFC 5869
-    $prk = hash_hmac('sha256', $licenseKey, $serverSecret, true);
+    // IKM: server_secret, Length: 32 bytes, Info: license_key
-
+    return bin2hex(hash_hkdf('sha256', $serverSecret, 32, $licenseKey));
-    return hash_hmac('sha256', $prk . "\x01", $serverSecret);
 }
 ```
 
+**Important:** This uses PHP's native `hash_hkdf()` function (available since PHP 7.1.2). The parameters are:
+
+- **Algorithm:** sha256
+- **IKM (Input Keying Material):** server_secret
+- **Length:** 32 bytes (256 bits)
+- **Info:** license_key (context-specific information)
+
 ### Response Signing
 
 Sign every API response before sending:
@@ -88,8 +96,8 @@ function sign_response(array $responseData, string $licenseKey, string $serverSe
     $timestamp = time();
     $signingKey = derive_signing_key($licenseKey, $serverSecret);
 
-    // Sort keys for consistent ordering
+    // Recursively sort keys for consistent ordering (important for nested arrays!)
-    ksort($responseData);
+    $responseData = recursive_key_sort($responseData);
 
     // Build signature payload
     $jsonBody = json_encode($responseData, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
@@ -103,6 +111,20 @@ function sign_response(array $responseData, string $licenseKey, string $serverSe
         'X-License-Timestamp' => (string) $timestamp,
     ];
 }
+
+/**
+ * Recursively sort array keys alphabetically.
+ */
+function recursive_key_sort(array $data): array
+{
+    ksort($data);
+    foreach ($data as $key => $value) {
+        if (is_array($value)) {
+            $data[$key] = recursive_key_sort($value);
+        }
+    }
+    return $data;
+}
 ```
 
 ### WordPress REST API Integration
@@ -214,7 +236,7 @@ class ResponseSigner
         $timestamp = time();
         $signingKey = $this->deriveKey($licenseKey);
 
-        ksort($data);
+        $data = $this->recursiveKeySort($data);
         $payload = $timestamp . ':' . json_encode(
             $data,
             JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE
@@ -226,11 +248,21 @@ class ResponseSigner
         ];
     }
 
+    private function recursiveKeySort(array $data): array
+    {
+        ksort($data);
+        foreach ($data as $key => $value) {
+            if (is_array($value)) {
+                $data[$key] = $this->recursiveKeySort($value);
+            }
+        }
+        return $data;
+    }
+
     private function deriveKey(string $licenseKey): string
     {
-        $prk = hash_hmac('sha256', $licenseKey, $this->serverSecret, true);
+        // HKDF key derivation per RFC 5869
-
+        return bin2hex(hash_hkdf('sha256', $this->serverSecret, 32, $licenseKey));
-        return hash_hmac('sha256', $prk . "\x01", $this->serverSecret);
     }
 }
 
@@ -262,8 +294,8 @@ signature = HMAC-SHA256(
 
 Where:
 
-- `derive_signing_key` uses HKDF-like derivation (see above)
+- `derive_signing_key` uses RFC 5869 HKDF: `hash_hkdf('sha256', server_secret, 32, license_key)`
-- `canonical_json` sorts keys alphabetically, no escaping of slashes/unicode
+- `canonical_json` recursively sorts keys alphabetically, no escaping of slashes/unicode
 - Result is hex-encoded (64 characters)
 
 ## Testing

releases/wc-licensed-product-0.7.1.zip.sha256

@@ -0,0 +1 @@
+6ffd0bdf47395436bbc28a029eff4c6d065f2b5b64c687b96ae36a74c3ee34ef  wc-licensed-product-0.7.1.zip

src/Admin/SettingsController.php

@@ -65,6 +65,7 @@ final class SettingsController
             'auto-updates' => __('Auto-Updates', 'wc-licensed-product'),
             'defaults' => __('Default Settings', 'wc-licensed-product'),
             'notifications' => __('Notifications', 'wc-licensed-product'),
+            'metrics' => __('Metrics', 'wc-licensed-product'),
         ];
     }
 
@@ -116,6 +117,7 @@ final class SettingsController
             'auto-updates' => $this->getAutoUpdatesSettings(),
             'defaults' => $this->getDefaultsSettings(),
             'notifications' => $this->getNotificationsSettings(),
+            'metrics' => $this->getMetricsSettings(),
             default => $this->getPluginLicenseSettings(),
         };
     }
@@ -314,6 +316,32 @@ final class SettingsController
         ];
     }
 
+    /**
+     * Get metrics settings
+     */
+    private function getMetricsSettings(): array
+    {
+        return [
+            'metrics_section_title' => [
+                'name' => __('Prometheus Metrics', 'wc-licensed-product'),
+                'type' => 'title',
+                'desc' => __('Expose license and API metrics for Prometheus monitoring. Requires the WP Prometheus plugin to be installed and active.', 'wc-licensed-product'),
+                'id' => 'wc_licensed_product_section_metrics',
+            ],
+            'metrics_enabled' => [
+                'name' => __('Enable Prometheus Metrics', 'wc-licensed-product'),
+                'type' => 'checkbox',
+                'desc' => __('Expose license statistics, API usage, and download metrics via Prometheus.', 'wc-licensed-product'),
+                'id' => 'wc_licensed_product_metrics_enabled',
+                'default' => 'no',
+            ],
+            'metrics_section_end' => [
+                'type' => 'sectionend',
+                'id' => 'wc_licensed_product_section_metrics_end',
+            ],
+        ];
+    }
+
     /**
      * Render settings tab content
      */
@@ -575,4 +603,12 @@ final class SettingsController
             wp_send_json_error(['message' => $error]);
         }
     }
+
+    /**
+     * Check if Prometheus metrics are enabled
+     */
+    public static function isMetricsEnabled(): bool
+    {
+        return get_option('wc_licensed_product_metrics_enabled', 'no') === 'yes';
+    }
 }

src/Api/ResponseSigner.php

@@ -26,9 +26,7 @@ final class ResponseSigner
 
     public function __construct()
     {
-        $this->serverSecret = defined('WC_LICENSE_SERVER_SECRET')
+        $this->serverSecret = self::getServerSecret();
-            ? WC_LICENSE_SERVER_SECRET
-            : '';
     }
 
     /**
@@ -79,7 +77,8 @@ final class ResponseSigner
 
         return str_starts_with($route, '/wc-licensed-product/v1/validate')
             || str_starts_with($route, '/wc-licensed-product/v1/status')
-            || str_starts_with($route, '/wc-licensed-product/v1/activate');
+            || str_starts_with($route, '/wc-licensed-product/v1/activate')
+            || str_starts_with($route, '/wc-licensed-product/v1/update-check');
     }
 
     /**
@@ -184,7 +183,7 @@ final class ResponseSigner
      */
     public static function getCustomerSecretForLicense(string $licenseKey): ?string
     {
-        $serverSecret = defined('WC_LICENSE_SERVER_SECRET') ? WC_LICENSE_SERVER_SECRET : '';
+        $serverSecret = self::getServerSecret();
 
         if (empty($serverSecret)) {
             return null;
@@ -200,6 +199,40 @@ final class ResponseSigner
      */
     public static function isSigningEnabled(): bool
     {
-        return defined('WC_LICENSE_SERVER_SECRET') && !empty(WC_LICENSE_SERVER_SECRET);
+        return !empty(self::getServerSecret());
+    }
+
+    /**
+     * Get the server secret from constant or environment variable
+     *
+     * Checks in order:
+     * 1. WC_LICENSE_SERVER_SECRET constant (preferred)
+     * 2. WC_LICENSE_SERVER_SECRET environment variable (Docker fallback)
+     *
+     * @return string The server secret, or empty string if not configured
+     */
+    public static function getServerSecret(): string
+    {
+        // First check the constant (standard WordPress configuration)
+        if (defined('WC_LICENSE_SERVER_SECRET') && !empty(WC_LICENSE_SERVER_SECRET)) {
+            return WC_LICENSE_SERVER_SECRET;
+        }
+
+        // Fallback to environment variable (Docker environments)
+        $envSecret = getenv('WC_LICENSE_SERVER_SECRET');
+        if ($envSecret !== false && !empty($envSecret)) {
+            return $envSecret;
+        }
+
+        // Also check $_ENV and $_SERVER (some PHP configurations)
+        if (!empty($_ENV['WC_LICENSE_SERVER_SECRET'])) {
+            return $_ENV['WC_LICENSE_SERVER_SECRET'];
+        }
+
+        if (!empty($_SERVER['WC_LICENSE_SERVER_SECRET'])) {
+            return $_SERVER['WC_LICENSE_SERVER_SECRET'];
+        }
+
+        return '';
     }
 }

src/Api/RestApiController.php

@@ -10,6 +10,7 @@ declare(strict_types=1);
 namespace Jeremias\WcLicensedProduct\Api;
 
 use Jeremias\WcLicensedProduct\License\LicenseManager;
+use Jeremias\WcLicensedProduct\Metrics\PrometheusController;
 use WP_REST_Request;
 use WP_REST_Response;
 use WP_REST_Server;
@@ -108,6 +109,10 @@ final class RestApiController
                 'retry_after' => $retryAfter,
             ], 429);
             $response->header('Retry-After', (string) $retryAfter);
+
+            // Track rate limit event for metrics
+            PrometheusController::incrementRateLimitExceeded('api');
+
             return $response;
         }
 
@@ -209,6 +214,16 @@ final class RestApiController
 
         $statusCode = $this->getStatusCodeForResult($result);
 
+        // Track metrics
+        if ($result['valid']) {
+            PrometheusController::incrementApiRequest('validate', 'success');
+        } else {
+            PrometheusController::incrementApiRequest('validate', 'error');
+            if (!empty($result['error'])) {
+                PrometheusController::incrementValidationError($result['error']);
+            }
+        }
+
         return new WP_REST_Response($result, $statusCode);
     }
 
@@ -247,6 +262,9 @@ final class RestApiController
         $license = $this->licenseManager->getLicenseByKey($licenseKey);
 
         if (!$license) {
+            PrometheusController::incrementApiRequest('status', 'error');
+            PrometheusController::incrementValidationError('license_not_found');
+
             return new WP_REST_Response([
                 'valid' => false,
                 'error' => 'license_not_found',
@@ -254,6 +272,8 @@ final class RestApiController
             ], 404);
         }
 
+        PrometheusController::incrementApiRequest('status', 'success');
+
         return new WP_REST_Response([
             'valid' => $license->isValid(),
             'status' => $license->getStatus(),
@@ -280,6 +300,9 @@ final class RestApiController
         $license = $this->licenseManager->getLicenseByKey($licenseKey);
 
         if (!$license) {
+            PrometheusController::incrementApiRequest('activate', 'error');
+            PrometheusController::incrementValidationError('license_not_found');
+
             return new WP_REST_Response([
                 'success' => false,
                 'error' => 'license_not_found',
@@ -288,6 +311,9 @@ final class RestApiController
         }
 
         if (!$license->isValid()) {
+            PrometheusController::incrementApiRequest('activate', 'error');
+            PrometheusController::incrementValidationError('license_invalid');
+
             return new WP_REST_Response([
                 'success' => false,
                 'error' => 'license_invalid',
@@ -299,6 +325,8 @@ final class RestApiController
 
         // Check if already activated on this domain
         if ($license->getDomain() === $normalizedDomain) {
+            PrometheusController::incrementApiRequest('activate', 'success');
+
             return new WP_REST_Response([
                 'success' => true,
                 'message' => __('License is already activated for this domain.', 'wc-licensed-product'),
@@ -307,6 +335,9 @@ final class RestApiController
 
         // Check if can activate on another domain
         if (!$license->canActivate()) {
+            PrometheusController::incrementApiRequest('activate', 'error');
+            PrometheusController::incrementValidationError('max_activations_reached');
+
             return new WP_REST_Response([
                 'success' => false,
                 'error' => 'max_activations_reached',
@@ -318,6 +349,9 @@ final class RestApiController
         $success = $this->licenseManager->updateLicenseDomain($license->getId(), $domain);
 
         if (!$success) {
+            PrometheusController::incrementApiRequest('activate', 'error');
+            PrometheusController::incrementValidationError('activation_failed');
+
             return new WP_REST_Response([
                 'success' => false,
                 'error' => 'activation_failed',
@@ -325,6 +359,8 @@ final class RestApiController
             ], 500);
         }
 
+        PrometheusController::incrementApiRequest('activate', 'success');
+
         return new WP_REST_Response([
             'success' => true,
             'message' => __('License activated successfully.', 'wc-licensed-product'),

src/Api/UpdateController.php

@@ -12,6 +12,7 @@ declare(strict_types=1);
 namespace Jeremias\WcLicensedProduct\Api;
 
 use Jeremias\WcLicensedProduct\License\LicenseManager;
+use Jeremias\WcLicensedProduct\Metrics\PrometheusController;
 use Jeremias\WcLicensedProduct\Product\VersionManager;
 use Jeremias\WcLicensedProduct\Product\ProductVersion;
 use WP_REST_Request;
@@ -113,6 +114,10 @@ final class UpdateController
                 'retry_after' => $retryAfter,
             ], 429);
             $response->header('Retry-After', (string) $retryAfter);
+
+            // Track rate limit event for metrics
+            PrometheusController::incrementRateLimitExceeded('update-check');
+
             return $response;
         }
 
@@ -179,10 +184,14 @@ final class UpdateController
         $validationResult = $this->licenseManager->validateLicense($licenseKey, $domain);
 
         if (!$validationResult['valid']) {
+            $errorType = $validationResult['error'] ?? 'license_invalid';
+            PrometheusController::incrementApiRequest('update-check', 'error');
+            PrometheusController::incrementValidationError($errorType);
+
             return new WP_REST_Response([
                 'success' => false,
                 'update_available' => false,
-                'error' => $validationResult['error'] ?? 'license_invalid',
+                'error' => $errorType,
                 'message' => $validationResult['message'] ?? __('License validation failed.', 'wc-licensed-product'),
             ], $validationResult['error'] === 'license_not_found' ? 404 : 403);
         }
@@ -190,6 +199,9 @@ final class UpdateController
         // Get license to access product ID
         $license = $this->licenseManager->getLicenseByKey($licenseKey);
         if (!$license) {
+            PrometheusController::incrementApiRequest('update-check', 'error');
+            PrometheusController::incrementValidationError('license_not_found');
+
             return new WP_REST_Response([
                 'success' => false,
                 'update_available' => false,
@@ -202,6 +214,9 @@ final class UpdateController
         $product = wc_get_product($productId);
 
         if (!$product) {
+            PrometheusController::incrementApiRequest('update-check', 'error');
+            PrometheusController::incrementValidationError('product_not_found');
+
             return new WP_REST_Response([
                 'success' => false,
                 'update_available' => false,
@@ -214,6 +229,8 @@ final class UpdateController
         $latestVersion = $this->getLatestVersionForLicense($license);
 
         if (!$latestVersion) {
+            PrometheusController::incrementApiRequest('update-check', 'success');
+
             return new WP_REST_Response([
                 'success' => true,
                 'update_available' => false,
@@ -230,6 +247,8 @@ final class UpdateController
         // Build response
         $response = $this->buildUpdateResponse($product, $latestVersion, $license, $updateAvailable);
 
+        PrometheusController::incrementApiRequest('update-check', 'success');
+
         return new WP_REST_Response($response);
     }
 

src/Frontend/AccountController.php

@@ -428,6 +428,26 @@ final class AccountController
                                         ?>
                                     </span>
                                 </div>
+                                <?php if (ResponseSigner::isSigningEnabled() && !empty($license['customer_secret'])): ?>
+                                    <div class="license-row-secret">
+                                        <button type="button" class="secret-toggle" aria-expanded="false">
+                                            <span class="dashicons dashicons-lock"></span>
+                                            <?php esc_html_e('API Verification Secret', 'wc-licensed-product'); ?>
+                                            <span class="dashicons dashicons-arrow-down-alt2 toggle-arrow"></span>
+                                        </button>
+                                        <div class="secret-content" style="display: none;">
+                                            <p class="secret-description">
+                                                <?php esc_html_e('Use this secret to verify signed API responses. Keep it secure.', 'wc-licensed-product'); ?>
+                                            </p>
+                                            <div class="secret-value-wrapper">
+                                                <code class="secret-value"><?php echo esc_html($license['customer_secret']); ?></code>
+                                                <button type="button" class="copy-secret-btn" data-secret="<?php echo esc_attr($license['customer_secret']); ?>" title="<?php esc_attr_e('Copy to clipboard', 'wc-licensed-product'); ?>">
+                                                    <span class="dashicons dashicons-clipboard"></span>
+                                                </button>
+                                            </div>
+                                        </div>
+                                    </div>
+                                <?php endif; ?>
                             </div>
                         <?php endforeach; ?>
                     </div>

src/Metrics/PrometheusController.php

@@ -0,0 +1,259 @@
+<?php
+/**
+ * Prometheus Metrics Controller
+ *
+ * @package Jeremias\WcLicensedProduct\Metrics
+ */
+
+declare(strict_types=1);
+
+namespace Jeremias\WcLicensedProduct\Metrics;
+
+use Jeremias\WcLicensedProduct\Admin\SettingsController;
+use Jeremias\WcLicensedProduct\License\LicenseManager;
+use Jeremias\WcLicensedProduct\Product\VersionManager;
+
+/**
+ * Exposes license and API metrics for Prometheus monitoring
+ */
+final class PrometheusController
+{
+    /**
+     * Option name for storing API counters
+     */
+    private const COUNTERS_OPTION = 'wclp_prometheus_counters';
+
+    private LicenseManager $licenseManager;
+    private VersionManager $versionManager;
+
+    public function __construct(LicenseManager $licenseManager, VersionManager $versionManager)
+    {
+        $this->licenseManager = $licenseManager;
+        $this->versionManager = $versionManager;
+    }
+
+    /**
+     * Register hooks for Prometheus metrics collection
+     */
+    public function register(): void
+    {
+        // Only register if metrics are enabled
+        if (!SettingsController::isMetricsEnabled()) {
+            return;
+        }
+
+        add_action('wp_prometheus_collect_metrics', [$this, 'collectMetrics']);
+    }
+
+    /**
+     * Collect and register all metrics
+     *
+     * @param object $collector The Prometheus collector object
+     */
+    public function collectMetrics(object $collector): void
+    {
+        $this->collectLicenseMetrics($collector);
+        $this->collectDownloadMetrics($collector);
+        $this->collectApiMetrics($collector);
+    }
+
+    /**
+     * Collect license-related metrics
+     */
+    private function collectLicenseMetrics(object $collector): void
+    {
+        $stats = $this->licenseManager->getStatistics();
+
+        // License count by status (gauge)
+        $licensesByStatus = $collector->register_gauge(
+            'wclp_licenses_total',
+            'Total number of licenses by status',
+            ['status']
+        );
+
+        foreach ($stats['by_status'] as $status => $count) {
+            $licensesByStatus->set($count, [$status]);
+        }
+
+        // Lifetime licenses (gauge)
+        $lifetimeLicenses = $collector->register_gauge(
+            'wclp_licenses_lifetime_total',
+            'Total number of lifetime licenses'
+        );
+        $lifetimeLicenses->set($stats['lifetime']);
+
+        // Expiring licenses (gauge)
+        $expiringLicenses = $collector->register_gauge(
+            'wclp_licenses_expiring_total',
+            'Total number of licenses with expiration date'
+        );
+        $expiringLicenses->set($stats['expiring']);
+
+        // Licenses expiring soon - next 30 days (gauge)
+        $expiringSoon = $collector->register_gauge(
+            'wclp_licenses_expiring_soon',
+            'Licenses expiring within 30 days'
+        );
+        $expiringSoon->set($stats['expiring_soon']);
+    }
+
+    /**
+     * Collect download-related metrics
+     */
+    private function collectDownloadMetrics(object $collector): void
+    {
+        $stats = $this->versionManager->getDownloadStatistics();
+
+        // Total downloads (gauge)
+        $totalDownloads = $collector->register_gauge(
+            'wclp_downloads_total',
+            'Total number of file downloads'
+        );
+        $totalDownloads->set($stats['total']);
+
+        // Active versions count (gauge)
+        $activeVersions = $collector->register_gauge(
+            'wclp_versions_active_total',
+            'Total number of active product versions'
+        );
+        $activeVersions->set($this->countActiveVersions());
+    }
+
+    /**
+     * Collect API-related metrics (counters)
+     */
+    private function collectApiMetrics(object $collector): void
+    {
+        $counters = $this->getCounters();
+
+        // API requests by endpoint and result (counter)
+        $apiRequests = $collector->register_counter(
+            'wclp_api_requests_total',
+            'Total API requests by endpoint and result',
+            ['endpoint', 'result']
+        );
+
+        foreach ($counters['api_requests'] ?? [] as $key => $count) {
+            [$endpoint, $result] = explode(':', $key);
+            $apiRequests->incBy($count, [$endpoint, $result]);
+        }
+
+        // Rate limit exceeded events (counter)
+        $rateLimitExceeded = $collector->register_counter(
+            'wclp_rate_limit_exceeded_total',
+            'Total rate limit exceeded events by endpoint',
+            ['endpoint']
+        );
+
+        foreach ($counters['rate_limit'] ?? [] as $endpoint => $count) {
+            $rateLimitExceeded->incBy($count, [$endpoint]);
+        }
+
+        // Validation errors by type (counter)
+        $validationErrors = $collector->register_counter(
+            'wclp_validation_errors_total',
+            'Total validation errors by error type',
+            ['error_type']
+        );
+
+        foreach ($counters['validation_errors'] ?? [] as $errorType => $count) {
+            $validationErrors->incBy($count, [$errorType]);
+        }
+    }
+
+    /**
+     * Count active product versions
+     */
+    private function countActiveVersions(): int
+    {
+        global $wpdb;
+
+        $tableName = \Jeremias\WcLicensedProduct\Installer::getVersionsTable();
+
+        return (int) $wpdb->get_var(
+            "SELECT COUNT(*) FROM {$tableName} WHERE is_active = 1"
+        );
+    }
+
+    /**
+     * Get stored counters
+     */
+    private function getCounters(): array
+    {
+        $counters = get_option(self::COUNTERS_OPTION, []);
+        return is_array($counters) ? $counters : [];
+    }
+
+    /**
+     * Increment an API request counter
+     *
+     * @param string $endpoint The API endpoint (validate, status, activate, update-check)
+     * @param string $result The result (success or error)
+     */
+    public static function incrementApiRequest(string $endpoint, string $result): void
+    {
+        if (!SettingsController::isMetricsEnabled()) {
+            return;
+        }
+
+        $counters = get_option(self::COUNTERS_OPTION, []);
+        if (!is_array($counters)) {
+            $counters = [];
+        }
+
+        $key = "{$endpoint}:{$result}";
+        $counters['api_requests'][$key] = ($counters['api_requests'][$key] ?? 0) + 1;
+
+        update_option(self::COUNTERS_OPTION, $counters, false);
+    }
+
+    /**
+     * Increment rate limit exceeded counter
+     *
+     * @param string $endpoint The API endpoint
+     */
+    public static function incrementRateLimitExceeded(string $endpoint): void
+    {
+        if (!SettingsController::isMetricsEnabled()) {
+            return;
+        }
+
+        $counters = get_option(self::COUNTERS_OPTION, []);
+        if (!is_array($counters)) {
+            $counters = [];
+        }
+
+        $counters['rate_limit'][$endpoint] = ($counters['rate_limit'][$endpoint] ?? 0) + 1;
+
+        update_option(self::COUNTERS_OPTION, $counters, false);
+    }
+
+    /**
+     * Increment validation error counter
+     *
+     * @param string $errorType The error type (license_not_found, domain_mismatch, etc.)
+     */
+    public static function incrementValidationError(string $errorType): void
+    {
+        if (!SettingsController::isMetricsEnabled()) {
+            return;
+        }
+
+        $counters = get_option(self::COUNTERS_OPTION, []);
+        if (!is_array($counters)) {
+            $counters = [];
+        }
+
+        $counters['validation_errors'][$errorType] = ($counters['validation_errors'][$errorType] ?? 0) + 1;
+
+        update_option(self::COUNTERS_OPTION, $counters, false);
+    }
+
+    /**
+     * Reset all counters (useful for testing or maintenance)
+     */
+    public static function resetCounters(): void
+    {
+        delete_option(self::COUNTERS_OPTION);
+    }
+}

src/Plugin.php

@@ -26,6 +26,7 @@ use Jeremias\WcLicensedProduct\Frontend\AccountController;
 use Jeremias\WcLicensedProduct\Frontend\DownloadController;
 use Jeremias\WcLicensedProduct\License\LicenseManager;
 use Jeremias\WcLicensedProduct\License\PluginLicenseChecker;
+use Jeremias\WcLicensedProduct\Metrics\PrometheusController;
 use Jeremias\WcLicensedProduct\Product\LicensedProductType;
 use Jeremias\WcLicensedProduct\Product\VersionManager;
 use Jeremias\WcLicensedProduct\Update\PluginUpdateChecker;
@@ -147,7 +148,7 @@ final class Plugin
         new LicenseEmailController($this->licenseManager);
 
         // Initialize response signing if server secret is configured
-        if (defined('WC_LICENSE_SERVER_SECRET') && WC_LICENSE_SERVER_SECRET !== '') {
+        if (ResponseSigner::isSigningEnabled()) {
             (new ResponseSigner())->register();
         }
 
@@ -171,6 +172,9 @@ final class Plugin
         if (!empty($serverUrl) && !$licenseChecker->isSelfLicensing()) {
             PluginUpdateChecker::getInstance()->register();
         }
+
+        // Initialize Prometheus metrics if enabled
+        (new PrometheusController($this->licenseManager, $this->versionManager))->register();
     }
 
     /**

wc-licensed-product.php

@@ -3,7 +3,7 @@
  * Plugin Name: WooCommerce Licensed Product
  * Plugin URI: https://src.bundespruefstelle.ch/magdev/wc-licensed-product
  * Description: WooCommerce plugin to sell software products using license keys with domain-based validation.
- * Version: 0.7.0
+ * Version: 0.7.4
  * Author: Marco Graetsch
  * Author URI: https://src.bundespruefstelle.ch/magdev
  * License: GPL-2.0-or-later
@@ -28,7 +28,7 @@ if (!defined('ABSPATH')) {
 }
 
 // Plugin constants
-define('WC_LICENSED_PRODUCT_VERSION', '0.7.0');
+define('WC_LICENSED_PRODUCT_VERSION', '0.7.4');
 define('WC_LICENSED_PRODUCT_PLUGIN_FILE', __FILE__);
 define('WC_LICENSED_PRODUCT_PLUGIN_DIR', plugin_dir_path(__FILE__));
 define('WC_LICENSED_PRODUCT_PLUGIN_URL', plugin_dir_url(__FILE__));