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fix(artifacts): stop artifact blobs opening as scriptable documents - #514
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openBase64InNewTab built the blob with the artifact's own MIME type and handed it to window.open. A blob URL inherits the origin of the page that created it, so a text/html or image/svg+xml artifact opened in a tab ran with the Dev UI's origin and a live window.opener handle back into the session. Artifact bytes are untrusted: an agent, a tool, or an upload produces them. Downgrade the blob type to application/octet-stream for MIME types the browser parses into a scriptable document, so those artifacts download rather than render. Inert types are unchanged.
This was referenced Aug 26, 2026
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GWeale
approved these changes
Aug 26, 2026
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openBase64InNewTab built the blob with the artifact's own MIME type and handed it to window.open. A blob URL inherits the origin of the page that created it, so a text/html or image/svg+xml artifact opened in a tab ran with the Dev UI's origin and a live window.opener handle back into the session. Artifact bytes are untrusted: an agent, a tool, or an upload produces them.
Downgrade the blob type to application/octet-stream for MIME types the browser parses into a scriptable document, so those artifacts download rather than render. Inert types are unchanged.