CVE-2025-11712: firefox Improper Encoding — Fix

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.

Is your site exposed to CVE-2025-11712?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

6.1

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Weakness Type (CWE)

CWE-116 CWE-116

Affected Products

Vendor	Product	Versions
mozilla	firefox	< 140.4.0
mozilla	firefox	< 144.0
mozilla	thunderbird	< 140.4.0
mozilla	thunderbird	141.0 — 144.0

References

Advisories & Patches

https://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/

Other References

https://bugzilla.mozilla.org/show_bug.cgi?id=1979536 https://lists.debian.org/debian-lts-announce/2025/10/msg00015.html https://lists.debian.org/debian-lts-announce/2025/10/msg00031.html

Frequently Asked Questions

What is CVE-2025-11712? +

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. It has a CVSS v3.1 base score of 6.1 (MEDIUM).

How severe is CVE-2025-11712? +

CVE-2025-11712 has a CVSS v3.1 score of 6.1 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-11712? +

CVE-2025-11712 affects products from mozilla, specifically: firefox, thunderbird. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-11712? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-45570

go-git is an extensible git implementation library written in pure Go. Prior to 5.19.1 and 6.0.0-alpha.4, go-git's SSH transport constructs …

CVE-2025-1795

During an address list folding when a separating comma ends up on a folded line and that line is to …

CVE-2025-32072

Improper Encoding or Escaping of Output vulnerability in The Wikimedia Foundation Mediawiki Core - Feed Utils allows WebView Injection.This issue …

CVE-2025-32078

Improper Encoding or Escaping of Output vulnerability in The Wikimedia Foundation Mediawiki - Version Compare Extension allows Cross-Site Scripting (XSS).This …

CVE-2025-1308

A vulnerability exists in PX Backup whereby sensitive information may be logged under specific conditions.

CVE-2025-34141

A reflected cross-site scripting (XSS) vulnerability exists in ETQ Reliance CG (legacy) platform within the `SQLConverterServlet` component. This vulnerability requires …

CVE-2025-11712