It was possible to craft an email that showed a tracking link as an attachment. If the user attempted to open the attachment, Thunderbird automatically accessed the link. The configuration to block remote content did not prevent that. Thunderbird has been fixed to no longer allow access to web pages listed in the X-Mozilla-External-Attachment-URL header of an email. This vulnerability affects Thunderbird < 128.10.1 and Thunderbird < 138.0.1.
The product requires authentication, but the product has an alternate path or channel that does not require authentication.
Link | Tags |
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https://bugzilla.mozilla.org/show_bug.cgi?id=1960412 | permissions required |
https://www.mozilla.org/security/advisories/mfsa2025-34/ | vendor advisory |
https://www.mozilla.org/security/advisories/mfsa2025-35/ | vendor advisory |