Trusted DOM and Sanitizing

Safe DOM boundaries for Markdown, descriptors and host content.

What it covers

Trusted DOM distinguishes plain text, validated attributes, structured node descriptors, and HTML fragments. textContent and node-based replaceChildren are preferred; innerHTML and insertAdjacentHTML require an explicit sanitizing boundary.

Public building blocks

• security/trusted-dom-policy.js classifies markup and DOM sinks.
• security/trusted-dom-policy.d.ts describes verdicts and sanitizer API.
• security/xss-pentest-policy.js contains negative URL, event, and markup cases.

Recommended workflow

Treat Markdown or Parsedown HTML as untrusted even when it lives in the repository, until sanitizeTrustedDomHtml() and the boundary return a positive verdict. Inline handlers, javascript: URLs, eval, and new Function remain forbidden. A sanitizer removes dangerous content; it does not turn arbitrary script sources into allowed modules. The browser proof exercises this boundary in a real DOM.

Next steps

• Manifest Import Policy
• Supply Chain checks