We use these services and cookies to improve your user experience. You may opt out if you wish, however, this may limit some features on this site.
Please see our statement on Data Privacy.
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.
Reserved 2025-04-25 | Published 2025-05-14 | Updated 2025-05-15 | Assigner mozillaTracking Links in Attachments Bypassed Remote Content Blocking
Dario Weißer
bugzilla.mozilla.org/show_bug.cgi?id=1960412
www.mozilla.org/security/advisories/mfsa2025-34/
www.mozilla.org/security/advisories/mfsa2025-35/
Support options
