The previous _sanitizeHtml was a denylist over agent/transcript markdown
rendered via innerHTML; it missed style attributes and the svg/math mXSS
namespaces — e.g. <svg><style><img src=x onerror=alert(1)></style></svg>
re-serialized into a live <img onerror>.
Vendor DOMPurify 3.4.8 (allowlist) following the existing marked.min.js
vendor pattern (same-origin, CSP script-src 'self'; not in package.json so
no lockfile drift). New sanitize-html.js wires a hardened allowlist config
(FORBID style/svg/math/script/iframe/object/embed/form; no data attrs);
app.js _sanitizeHtml delegates to it with a fail-closed escape-all fallback.
index.html loads dompurify -> sanitize-html -> app.js (defer); build.mjs
minifies + content-hashes sanitize-html.js.
Test: test/markdown-sanitizer.test.ts (jsdom, real shipping artifacts) —
mXSS payloads neutralized + legit markdown preserved.
Add marked.js (39KB) for rich text display in the response viewer.
Renders headings, code blocks, lists, tables, blockquotes, and
inline formatting with dark theme styling.
Falls back to escaped plain text if marked.js fails to load.
Aamer Akhter