Description
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.
Affected products
mozilla: firefox; mozilla: thunderbird
References7
- www.mozilla.org/security/advisories/mfsa2025-81/ Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2025-83/ Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2025-84/ Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2025-85/ Vendor Advisory
- bugzilla.mozilla.org/show_bug.cgi?id=1979536 Issue TrackingPermissions Required
- lists.debian.org/debian-lts-announce/2025/10/msg00015.html
- lists.debian.org/debian-lts-announce/2025/10/msg00031.html
Metrics
- CVSS 3.1
-
6.1
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - EPSS — exploit probability
- 0% percentile: 13 · as of 9 November 2026
- CWE
- CWE-116
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