ZBBS-WORK-395: harden the admin mermaid note-render path against XSS#234
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The notes viewer's mermaid path was the one v-html sink fed from semi-trusted data (notes are authored by agents and the dream pipeline's LLM output) whose only sanitization was an implicit third-party default: mermaid 11.x's securityLevel defaulting to 'strict'. No app-level backstop, no CSP — a future 'loose' tweak or a mermaid sanitizer bypass (they have securityLevel-bypass CVEs in their history) would have been live stored XSS. Three coupled changes in notes.js: - Pin securityLevel: 'strict' explicitly so it can't silently regress. - htmlLabels: false (+ flowchart.htmlLabels) — labels render as native SVG <text> instead of foreignObject+XHTML. Verified empirically against the repo's exact dists (mermaid 11.15.0 / dompurify 3.4.8, headless Firefox): with HTML labels on, the SVG sanitize profile destroys every flowchart label, and re-allowing foreignObject still loses its HTML children to DOMPurify's namespace rules. Pure-SVG output sanitizes losslessly (flowchart 124->124, sequence 64->64, adversarial 81->81 elements; payloads survive only as inert escaped label text; DOM scan shows no on* attrs / script / javascript: URLs). - App-level DOMPurify pass (SVG profiles) on mermaid's output before the v-html assignment, mirroring the markdown path's belt-and-suspenders. code_review 1 round: no blocking issues, ship as-is. Pre-existing non-blockers left untouched: the error-fallback <pre> construction and the Date.now() render-id (collision-prone only sub-millisecond). CSP for the admin app remains the ticket's deferred item 3. Frontend-only; no migration. vite build:admin passes. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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…234) The notes viewer's mermaid path was the one v-html sink fed from semi-trusted data (notes are authored by agents and the dream pipeline's LLM output) whose only sanitization was an implicit third-party default: mermaid 11.x's securityLevel defaulting to 'strict'. No app-level backstop, no CSP — a future 'loose' tweak or a mermaid sanitizer bypass (they have securityLevel-bypass CVEs in their history) would have been live stored XSS. Three coupled changes in notes.js: - Pin securityLevel: 'strict' explicitly so it can't silently regress. - htmlLabels: false (+ flowchart.htmlLabels) — labels render as native SVG <text> instead of foreignObject+XHTML. Verified empirically against the repo's exact dists (mermaid 11.15.0 / dompurify 3.4.8, headless Firefox): with HTML labels on, the SVG sanitize profile destroys every flowchart label, and re-allowing foreignObject still loses its HTML children to DOMPurify's namespace rules. Pure-SVG output sanitizes losslessly (flowchart 124->124, sequence 64->64, adversarial 81->81 elements; payloads survive only as inert escaped label text; DOM scan shows no on* attrs / script / javascript: URLs). - App-level DOMPurify pass (SVG profiles) on mermaid's output before the v-html assignment, mirroring the markdown path's belt-and-suspenders. code_review 1 round: no blocking issues, ship as-is. Pre-existing non-blockers left untouched: the error-fallback <pre> construction and the Date.now() render-id (collision-prone only sub-millisecond). CSP for the admin app remains the ticket's deferred item 3. Frontend-only; no migration. vite build:admin passes. Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
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Why
The notes viewer's mermaid path is the one
v-htmlsink in the admin SPA fed from semi-trusted data (notes come from agents and the dream pipeline's LLM output). Its only sanitization was mermaid's implicitsecurityLevel: 'strict'default — a single point of failure with bypass CVEs in its history, one careless 'loose' tweak away from stored XSS, with no CSP behind it. Full audit inshared/tasks/pending/zbbs-work-395-admin-mermaid-xss-hardening(all other render surfaces verified framework-escaped).What
In notes.js, three coupled changes:
securityLevel: 'strict'so a regression is a visible diff line.htmlLabels: false— labels become native SVG<text>. Required for the next piece: verified against the repo's exact dists in headless Firefox that with HTML labels on, the SVG sanitize profile destroys every flowchart label, and re-allowingforeignObjectstill loses its HTML children to DOMPurify's namespace rules.DOMPurify.sanitize(svg, { USE_PROFILES: { svg: true, svgFilters: true } })before the v-html assignment — belt-and-suspenders matching the markdown path.Verified lossless on flowchart / sequence / adversarial-payload diagrams (zero element loss, labels intact, payloads inert as escaped text, DOM scan clean of on*/script/javascript:).
vite build:adminpasses. Frontend-only, no migration.code_review: 1 round, no blocking issues. CSP for the admin app stays deferred (ticket item 3).
— Work
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