Update CLAUDE.md with v0.3.6 session history

- Document security hardening changes (CSRF, IP spoofing, XSS)
- Add recursive key sorting fix for response signing
- Document trusted proxy configuration
- Add release information (SHA256, package size)

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

CLAUDE.md

@@ -36,7 +36,7 @@ This project is proudly **"vibe-coded"** using Claude.AI - the entire codebase w
 
 No known bugs at the moment.
 
-### Version 0.3.6
+### Version 0.3.7
 
 No changes at the moment.
 
@@ -978,3 +978,57 @@ Added admin dashboard widget for license statistics and automatic license expira
 - `autoExpireLicense()` updates status to expired and returns true if changed
 - LicenseExpiredEmail follows same pattern as LicenseExpirationEmail (warning vs expired)
 - Expired notification tracked via user meta to prevent duplicate emails
+
+### 2026-01-23 - Version 0.3.6 - Security Hardening
+
+**Overview:**
+
+Security audit and implementation alignment with client/server documentation. Fixed response signing compatibility, rate limiting security, and XSS prevention.
+
+**Security Fixes:**
+
+- Added CSRF protection (nonce verification) to CSV export functionality
+- Fixed IP header spoofing vulnerability in rate limiting - now requires explicit trusted proxy configuration
+- Enabled explicit Twig autoescape (`'html'`) for XSS protection
+- Fixed unescaped status values in CSS class names in Twig templates
+
+**Implementation Fixes:**
+
+- Fixed response signing to use recursive key sorting for client library compatibility
+- ResponseSigner now recursively sorts nested array keys alphabetically as required by `magdev/wc-licensed-product-client`
+
+**Modified files:**
+
+- `src/Api/ResponseSigner.php` - Added `recursiveKeySort()` method for proper signature generation
+- `src/Api/RestApiController.php` - Added trusted proxy support with `isTrustedProxy()`, `isCloudflareIp()`, `ipMatchesCidr()` methods
+- `src/Plugin.php` - Added explicit `autoescape => 'html'` to Twig environment
+- `src/Admin/AdminController.php` - Added nonce verification to `handleCsvExport()`, added `export_csv_url()` Twig function
+- `templates/frontend/licenses.html.twig` - Added `esc_attr()` for CSS class status
+- `templates/admin/licenses.html.twig` - Added `esc_attr()` for CSS class status, updated export link to use `export_csv_url()`
+
+**Configuration:**
+
+To enable trusted proxy support for rate limiting, add to `wp-config.php`:
+
+```php
+// For Cloudflare
+define('WC_LICENSE_TRUSTED_PROXIES', 'CLOUDFLARE');
+
+// Or for specific IPs/CIDR ranges
+define('WC_LICENSE_TRUSTED_PROXIES', '10.0.0.1,192.168.1.0/24');
+```
+
+**Technical notes:**
+
+- Rate limiting now only trusts proxy headers (`HTTP_CF_CONNECTING_IP`, `HTTP_X_FORWARDED_FOR`, `HTTP_X_REAL_IP`) when `WC_LICENSE_TRUSTED_PROXIES` constant is defined
+- Without trusted proxy configuration, rate limiting uses `REMOTE_ADDR` only (prevents IP spoofing)
+- Cloudflare IP ranges are hardcoded for convenience (as of 2024)
+- CIDR notation supported for custom proxy ranges
+- Recursive key sorting ensures signature compatibility with SecureLicenseClient
+- References: <https://src.bundespruefstelle.ch/magdev/wc-licensed-product-client/raw/branch/main/docs/server-implementation.md>
+
+**Release v0.3.6:**
+
+- Created release package: `releases/wc-licensed-product-0.3.6.zip` (818 KB)
+- SHA256: `b0063f0312759f090e12faba83de730baf4114139d763e46fad2b781d4b38270`
+- Tagged as `v0.3.6` and pushed to `main` branch