web-ui: sanitize markdown HTML with DOMPurify to fix XSS

Both mdNode implementations (agent UI app.js, dashboard common.js)
assigned marked.parse() output straight to innerHTML with no
sanitizer. marked v5+ dropped its built-in sanitize option, and there
was no DOMPurify anywhere in frontend/, so markdown containing raw
HTML/script tags rendered live in the browser.

Both sinks receive untrusted input in practice: the agent UI's mdNode
renders recv tool_result bodies, assistant prose, and send/ask/answer
payloads sourced from peer agents and matrix-relayed messages (the
documented prompt-injection adversary); the dashboard's mdNode renders
agent-authored .md files served verbatim by GET /api/state-file
(the endpoint validates path, not content). Since the per-agent UI and
dashboard are same-origin behind the gateway with operator-authority
endpoints (approve/spawn/rebuild/destroy/answer-question), injected
script would run with the operator's session.

Fix: DOMPurify.sanitize() the marked.parse() output at both sinks
before assigning to innerHTML. Added dompurify as a dependency to
both the agent and dashboard npm workspaces, recomputed npmDepsHash
in nix/frontend.nix for the updated lockfile. Also corrected
docs/web-ui/shape.md, which claimed the markdown-rendering path was
XSS-safe by construction the same way the text-node-based linkify
path is — it isn't; it's safe because it's sanitized.

CSP hardening for the dashboard (no unsafe-inline) is a separate,
larger backend change (response headers in hive-c0re) and is left as
a fast-follow rather than folded into this fix.
This commit is contained in:
iris 2026-07-10 02:46:51 +02:00 committed by mara
commit ccc5e631e2
7 changed files with 50 additions and 12 deletions

View file

@ -4,6 +4,7 @@
// infrastructure for the side panel.
import { linkify as termLinkify } from '@hive/shared/terminal.js';
import DOMPurify from 'dompurify';
// Themed dialog/toast helpers (modal.js imports `el` back from here — a safe
// deferred cycle: neither side uses the other at module-init time, only inside
// runtime handlers).
@ -543,12 +544,16 @@ function svgImage(text) {
return img;
}
// Marked-rendered markdown node (raw text fallback if `marked`
// failed to load).
// failed to load). `text` is untrusted (agent-authored state files served
// verbatim by /api/state-file) — the parsed HTML is run through DOMPurify
// before it touches innerHTML, since markdown can carry raw HTML/script
// tags that `marked` itself no longer strips (v5+ dropped the built-in
// sanitizer).
function mdNode(text) {
const div = el('div', { class: 'md' });
if (window.marked && typeof window.marked.parse === 'function') {
window.marked.setOptions({ breaks: true, gfm: true });
div.innerHTML = window.marked.parse(text);
div.innerHTML = DOMPurify.sanitize(window.marked.parse(text));
// marked autolinks URLs but leaves them same-tab — open externally
// so a click never navigates away from the dashboard.
div.querySelectorAll('a[href]').forEach((a) => {