Firefox & Thunderbird < 144 XSS via OBJECT type override
CVE-2025-11712 Published on October 14, 2025
An OBJECT tag type attribute overrode browser behavior on web resources without a content-type
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 affects Firefox < 144, Firefox ESR < 140.4, Thunderbird < 144, and Thunderbird < 140.4.
Vulnerability Analysis
CVE-2025-11712 is exploitable with network access, requires user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality and integrity, and no impact on availability.
Weakness Type
What is an Output Sanitization Vulnerability?
The software prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.
CVE-2025-11712 has been classified to as an Output Sanitization vulnerability or weakness.
Products Associated with CVE-2025-11712
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Affected Versions
Mozilla Firefox:- Version unspecified and below 144 is affected.
- Version unspecified and below 140.4 is affected.
- Version unspecified and below 144 is affected.
- Version unspecified and below 140.4 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.