Is Export Gemini Chats to PDF: Download & Archive Gemini Chats safe?

Export Gemini Chats to PDF accepts unchecked postMessage on gemini.google.com, letting any page trigger a silent, attacker-chosen download.

When exporting a chat as a PDF or image, the extension opens a hidden iframe on gemini.google.com and listens for a postMessage reply, but it never checks who sent that message. The background script then hands the message's dataUrl straight to chrome.downloads.download, and only values starting with "data:" are treated as the generated file — anything else, including an attacker-supplied URL, is fetched and saved to disk without a prompt. A page that opens a handle to the user's Gemini tab (for example via window.open) can exploit this to force a silent download while an export is in progress.

Part of this rating comes from analysis signals we haven't published as detailed findings yet.