security: OWASP audit and hardening (v1.0.8)

- Archive XSS: wrap get_the_archive_title/description with wp_kses_post()
  in ContextBuilder to sanitize Editor-editable term content rendered via |raw
- Comment fields: esc_html() on comment_author, esc_url() on comment_author_url
  at data source; template updated to output pre-escaped URL via |raw
- dark-mode.js: whitelist localStorage value against ['dark','light'] to
  prevent attribute injection from third-party script tampering
- TwigService: add is_safe=>html to esc_html/esc_attr/esc_url Twig functions
  to prevent double-encoding if autoescape is ever enabled
- Add .markdownlint.json (disable MD024 duplicate headings, MD013 line length)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.markdownlint.json

@@ -0,0 +1,4 @@
+{
+  "MD024": false,
+  "MD013": false
+}

CHANGELOG.md

@@ -2,6 +2,19 @@
 
 All notable changes to this project will be documented in this file.
 
+## [1.0.8] - 2026-02-19
+
+### Security
+
+- **Archive XSS hardening**: `ContextBuilder::getArchiveData()` now wraps `get_the_archive_title()` and `get_the_archive_description()` with `wp_kses_post()`. Term descriptions are user-editable by Editors and above; without sanitization an injected `<script>` tag would execute via the `|raw` filter in `archive.html.twig`
+- **Comment author XSS hardening**: `ContextBuilder::buildCommentTree()` now applies `esc_html()` to `comment_author` and `esc_url()` to `comment_author_url` at the data source, preventing injection via user-supplied comment fields
+- **Dark mode localStorage whitelist**: `getPreferredTheme()` in `dark-mode.js` now validates the stored theme value against `['dark', 'light']` before use, preventing attribute injection from a tampered localStorage value written by a third-party script
+- **Twig escaping functions marked safe**: `esc_html()`, `esc_attr()`, and `esc_url()` registered in `TwigService` are now declared with `['is_safe' => ['html']]`, preventing double-encoding if Twig autoescape is ever enabled
+
+### Changed
+
+- `views/partials/comment-item.html.twig`: Comment author URL now output via `{{ comment.author_url|raw }}` (escaped in PHP) instead of calling `esc_url()` from the template, keeping escaping logic in one place
+
 ## [1.0.7] - 2026-02-18
 
 ### Added

CLAUDE.md

@@ -211,6 +211,44 @@ Build steps (in order):
 
 ## Session History
 
+### Session 14 — v1.0.8 Security Audit & Hardening (2026-02-19)
+
+**Completed:** Comprehensive OWASP-aligned security audit. Two parallel background agents reviewed all PHP (functions.php, ContextBuilder, NavWalker, TemplateController, TwigService, all patterns) and JavaScript/Twig templates. Four targeted security fixes applied.
+
+**Findings and fixes:**
+
+- **Archive term description XSS (High)**: `get_the_archive_description()` returns raw term content editable by Editor-role users. Templates rendered it with `|raw`, creating a stored XSS path. Fixed: wrapped with `wp_kses_post()` in `ContextBuilder::getArchiveData()`. Same applied to `get_the_archive_title()`.
+- **Comment author injection (Low, defense-in-depth)**: `comment_author` and `comment_author_url` were passed to Twig as raw database values. Fixed: `esc_html()` applied to author name, `esc_url()` applied to author URL in `ContextBuilder::buildCommentTree()`. Template updated to output pre-escaped URL via `|raw` rather than calling `esc_url()` in Twig.
+- **Dark mode localStorage whitelist (Medium)**: `getPreferredTheme()` returned any stored value without validation, allowing attribute injection if a malicious script wrote to `localStorage`. Fixed: strict equality check against `['dark', 'light']` before trusting the stored value.
+- **Twig escaping functions not marked safe (Medium)**: `esc_html()`, `esc_attr()`, `esc_url()` registered in `TwigService` lacked `['is_safe' => ['html']]`, meaning any future autoescape enablement would cause double-encoding. Fixed: all three now carry the `is_safe` declaration.
+
+**Confirmed secure (no action needed):**
+
+- All `|raw` filter usages for widget HTML, comment content, comment reply links, and comment forms are by-design (WordPress core output)
+- Pattern files: no direct-access guards needed (loaded only via `register_block_pattern()`)
+- No SQL injection vectors (`$wpdb` not used directly; all data via WordPress functions)
+- `TemplateController` error handling: `\Throwable` caught, logged, and gated behind `WP_DEBUG`
+- `do_shortcode()` and `wp_kses_post()` Twig functions correctly marked `is_safe`
+- `wp_head()`, `wp_footer()`, `body_class()` Twig functions correctly use output buffering + `is_safe`
+
+**Key learnings:**
+
+- WordPress Twig themes should not enable `autoescape => 'html'` globally: `get_the_title()` applies `wptexturize()` which returns HTML entities (`—`, `“`). Autoescape would double-encode these, corrupting post title rendering.
+- `esc_url()` does more than HTML-encoding — it validates the URL scheme and strips dangerous protocols (`javascript:`, `data:`). Always use it for user-supplied URLs, even when autoescape is active.
+- Registering WordPress escaping functions (`esc_url`, `esc_html`, `esc_attr`) as Twig functions without `is_safe => html` silently creates a double-encoding trap: calling `{{ esc_url(url) }}` with autoescape on would produce `&` instead of `&`.
+- Added `.markdownlint.json` disabling MD024 (duplicate headings, expected in changelogs) and MD013 (line length).
+
+**Files modified:**
+
+- `inc/Template/ContextBuilder.php` — archive data sanitization, comment field escaping
+- `inc/Twig/TwigService.php` — `is_safe => html` on three escaping functions
+- `views/partials/comment-item.html.twig` — use pre-escaped author URL
+- `src/js/dark-mode.js` — localStorage whitelist
+- `assets/js/dark-mode.js` — rebuilt compiled output
+- `style.css` — version bump to 1.0.8
+- `CHANGELOG.md` — v1.0.8 entry
+- `.markdownlint.json` — created
+
 ### Session 13 — v1.0.5 Translation Files (2026-02-11)
 
 **Completed:** Standardized translation file naming and added 11 new locale translations.

assets/js/dark-mode.js

@@ -20,7 +20,9 @@
      */
     function getPreferredTheme() {
         var stored = localStorage.getItem(STORAGE_KEY);
-        if (stored) {
+        // Whitelist: only honour known-good values to prevent attribute injection
+        // from a tampered localStorage (e.g. XSS-written value by another script).
+        if (stored === 'dark' || stored === 'light') {
             return stored;
         }
         return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';

inc/Template/ContextBuilder.php

@@ -245,8 +245,10 @@ class ContextBuilder
     private function getArchiveData(): array
     {
         return [
-            'title'       => get_the_archive_title(),
-            'description' => get_the_archive_description(),
+            // wp_kses_post() allows safe HTML (headings, links, spans) while stripping
+            // script/event-handler attributes that could be injected via term descriptions.
+            'title'       => wp_kses_post(get_the_archive_title()),
+            'description' => wp_kses_post(get_the_archive_description()),
         ];
     }
 
@@ -291,8 +293,10 @@ class ContextBuilder
 
             $tree[] = [
                 'id'         => (int) $comment->comment_ID,
-                'author'     => $comment->comment_author,
-                'author_url' => $comment->comment_author_url,
+                // Escape at source — comment_author is user-supplied, store as safe text.
+                'author'     => esc_html($comment->comment_author),
+                // esc_url() strips dangerous schemes (javascript:, data:) and encodes for HTML.
+                'author_url' => esc_url($comment->comment_author_url),
                 'avatar_url' => get_avatar_url($comment, ['size' => 40]),
                 'date'       => get_comment_date('', $comment),
                 'date_iso'   => get_comment_date('c', $comment),

inc/Twig/TwigService.php

@@ -73,10 +73,12 @@ class TwigService
             return _n($single, $plural, $number, $domain);
         }));
 
-        // Escaping functions.
-        $this->twig->addFunction(new TwigFunction('esc_html', 'esc_html'));
-        $this->twig->addFunction(new TwigFunction('esc_attr', 'esc_attr'));
-        $this->twig->addFunction(new TwigFunction('esc_url', 'esc_url'));
+        // Escaping functions — marked is_safe so Twig does not double-escape their output.
+        // These functions already return HTML-safe strings; without is_safe, enabling
+        // Twig autoescape would double-encode the result (e.g. & → &).
+        $this->twig->addFunction(new TwigFunction('esc_html', 'esc_html', ['is_safe' => ['html']]));
+        $this->twig->addFunction(new TwigFunction('esc_attr', 'esc_attr', ['is_safe' => ['html']]));
+        $this->twig->addFunction(new TwigFunction('esc_url', 'esc_url', ['is_safe' => ['html']]));
 
         // WordPress head/footer output (captured via output buffering).
         $this->twig->addFunction(new TwigFunction('wp_head', function (): string {

src/js/dark-mode.js

@@ -20,7 +20,9 @@
      */
     function getPreferredTheme() {
         var stored = localStorage.getItem(STORAGE_KEY);
-        if (stored) {
+        // Whitelist: only honour known-good values to prevent attribute injection
+        // from a tampered localStorage (e.g. XSS-written value by another script).
+        if (stored === 'dark' || stored === 'light') {
             return stored;
         }
         return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';

style.css

@@ -7,7 +7,7 @@ Description: A modern WordPress Block Theme built from scratch with Bootstrap 5.
 Requires at least: 6.7
 Tested up to: 6.7
 Requires PHP: 8.3
-Version: 1.0.7
+Version: 1.0.8
 License: GNU General Public License v2 or later
 License URI: http://www.gnu.org/licenses/gpl-2.0.html
 Text Domain: wp-bootstrap

views/partials/comment-item.html.twig

@@ -7,7 +7,8 @@
         <div class="d-flex align-items-center gap-2 mb-1">
             <strong class="small">
                 {% if comment.author_url %}
-                    <a href="{{ esc_url(comment.author_url) }}" class="text-decoration-none text-body" rel="nofollow">
+                    {# author_url is pre-escaped with esc_url() in ContextBuilder #}
+                    <a href="{{ comment.author_url|raw }}" class="text-decoration-none text-body" rel="nofollow">
                         {{ comment.author }}
                     </a>
                 {% else %}