CVE-2025-11712
MediumCVSS 6.1Exploitation Probability (EPSS)
Low risk12th percentile - higher than 12% of all known CVEs
Summary
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. The vulnerability was fixed in Firefox 144, Firefox ESR 140.4, Thunderbird 144, and Thunderbird 140.4.
Risk Assessment
This could lead to execution of malicious script in the context of a vulnerable site, potentially enabling data or session theft. The risk applies to users of browsers and email clients with vulnerable versions.
Recommendation
Update Firefox, Firefox ESR, Thunderbird, and Thunderbird ESR to the patched versions (Firefox 144, Firefox ESR 140.4, Thunderbird 144, Thunderbird 140.4). Ensure proper content-type headers for served files.
Other vulnerabilities in Firefox
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Mozilla blocked compromised intermediate eMudhra certificates via OneCRL on October 17, and the list was distributed to clients via RemoteSettings the same day. This update contains the updated OneCRL block list, ensuring clients will block the compromised certificates even if RemoteSettings is disabled by policy or otherwise unavailable in the user's network environment. The vulnerability was fixed in Firefox 158.0.1, Firefox ESR 153.5.1, Firefox ESR 115.43.1, Thunderbird 158.0.1, and Thunderbird 153.5.1.
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Sandbox escape due to uninitialized memory in the DOM: Web Serial component. It was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
- CVE-2026-109740Critical
Sandbox escape due to incorrect boundary conditions in the Widget: Win32 component. The flaw was fixed in Firefox 158, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS