HTML passed to this library must be treated as untrusted input.

• Use a sandboxed iframe. The smallest useful policy is usually sandbox="allow-scripts" without allow-same-origin.
• Validate MessageEvent.source against the iframe's contentWindow before accepting any bridge message.
• Validate message payloads again in the host. Message names are routing hints, not authorization.
• Keep file, process, credential, clipboard, payment, and network authority outside the iframe.
• Pass external navigation through normalizeHtmlArtifactExternalUrl or an equally strict host policy.
• Apply a Content Security Policy appropriate for the host's threat model.

The generated iframe shell reports runtime errors but does not grant host capabilities. Its postMessage bridge is a request channel only.

Please avoid filing public exploit details before a fix is available. Contact the maintainer through the security reporting channel on the GitHub repository.