An OBJECT tag type attribute overrode browser behavior on web resources without a content-type
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.1epss 0.3%
exploitation probability
0.3%top 80% of all CVEs
observed exploitation
nono source reports it
A malicious page could have used the type attribute of an OBJECT tag to override the default browser behavior when encountering a web resource served without a content-type. This could have contributed to an XSS on a site that unsafely serves files without a content-type header. This vulnerability was fixed in Firefox 144, Firefox ESR 140.4, Thunderbird 144, and Thunderbird 140.4.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
References
https://bugzilla.mozilla.org/show_bug.cgi?id=1979536https://lists.debian.org/debian-lts-announce/2025/10/msg00015.htmlhttps://lists.debian.org/debian-lts-announce/2025/10/msg00031.htmlhttps://www.mozilla.org/security/advisories/mfsa2025-81/https://www.mozilla.org/security/advisories/mfsa2025-83/https://www.mozilla.org/security/advisories/mfsa2025-84/https://www.mozilla.org/security/advisories/mfsa2025-85/