The metadata Firefox is sending to Google about the unsigned binaries or binaries signed by an unstrusted party include [1]:

- The target URL from which the file was downloaded, its referrer URL and any URLs in the redirect chain.

- The SHA-256 hash of the contents of the file.

Because of privacy concerns I would rather this feature not be opt-out.

[1] https://wiki.mozilla.org/Security/Features/Application_Reput...