Mozilla Thunderbird up to 143 OBJECT Tag cross site scripting

Summaryinfo

A vulnerability categorized as problematic has been discovered in Mozilla Thunderbird up to 143. Affected by this issue is some unknown functionality of the component OBJECT Tag Handler. Executing a manipulation can lead to cross site scripting. This vulnerability is tracked as CVE-2025-11712. The attack can be launched remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Mozilla Thunderbird up to 143 and classified as problematic. This vulnerability affects an unknown functionality of the component OBJECT Tag Handler. The manipulation with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. CVE summarizes:

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.

The advisory is shared for download at bugzilla.mozilla.org. This vulnerability was named CVE-2025-11712 since 10/13/2025. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 11/16/2025). The MITRE ATT&CK project declares the attack technique as T1059.007.

The vulnerability scanner Nessus provides a plugin with the ID 270625 (Debian dsa-6025 : firefox-esr - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 144 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (270625) and CERT Bund (WID-SEC-2025-2275). Once again VulDB remains the best source for vulnerability data.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• RESF Rocky Linux
• IGEL OS
• Mozilla Firefox
• Mozilla Firefox ESR
• Mozilla Thunderbird

Productinfo

Type

• Mail Client Software

Vendor

• Mozilla

Name

• Thunderbird

Version

• 143

License

• open-source

Website

• Vendor: https://www.mozilla.org/

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Once again VulDB remains the best source for vulnerability data.

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