1. Path traversal in _serve_static() [CRITICAL]
Sandbox resolved path to static/ directory using relative_to().
GET /static/../../../../etc/passwd now returns 404.
2. Skill category path traversal [HIGH]
Validate category param in skill save: reject values with '/' or '..'.
3. Gate /api/approval/inject_test to loopback only [HIGH]
Endpoint now returns 404 for any non-127.0.0.1 client,
preserving test functionality while blocking remote access.
4. Escape captured groups in renderMd() [HIGH]
All inline markdown regexes (bold, italic, headings, blockquote,
list items, table cells/headers, link labels) now run captured
text through esc() before inserting into innerHTML, preventing
XSS via AI-generated content.
5. SRI hashes for CDN resources + pin Mermaid version [MEDIUM]
Added integrity= + crossorigin= to all three PrismJS CDN tags.
Pinned Mermaid from floating @10 to @10.9.3 with SRI hash.
Tests: 224 passed, 0 failed.
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