CVE-2025-5266: firefox Information Disclosure — Fix

Description

Script elements loading cross-origin resources generated load and error events which leaked information enabling XS-Leaks attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.

Is your site exposed to CVE-2025-5266?

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

CVSS v3.1 Score

4.3

MEDIUM

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

Weakness Type (CWE)

CWE-200 CWE-200

Affected Products

Vendor	Product	Versions
mozilla	firefox	< 128.11.0
mozilla	firefox	< 139.0

References

Advisories & Patches

https://www.mozilla.org/security/advisories/mfsa2025-42/ https://www.mozilla.org/security/advisories/mfsa2025-44/

Other References

https://bugzilla.mozilla.org/show_bug.cgi?id=1965628 https://www.mozilla.org/security/advisories/mfsa2025-45/ https://www.mozilla.org/security/advisories/mfsa2025-46/ https://lists.debian.org/debian-lts-announce/2025/05/msg00043.html https://lists.debian.org/debian-lts-announce/2025/05/msg00046.html

Frequently Asked Questions

What is CVE-2025-5266? +

Script elements loading cross-origin resources generated load and error events which leaked information enabling XS-Leaks attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2025-5266? +

CVE-2025-5266 has a CVSS v3.1 score of 4.3 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-2025-5266? +

CVE-2025-5266 affects products from mozilla, specifically: firefox. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-5266? +

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-2025-15625

Unauthenticated user is able to execute arbitrary SQL commands in Sparx Pro Cloud Server database in certain cases.

CVE-2026-22051

StorageGRID (formerly StorageGRID Webscale) versions prior to 11.9.0.13 and 12.0.0.6 are susceptible to a Information Disclosure vulnerability. Successful exploit could …

CVE-2026-54396

An information disclosure vulnerability exists in the MISP AuthKey edit functionality. When a validation error occurs during an AuthKey edit …

CVE-2026-13230

An information disclosure vulnerability was identified in TP-Link Kasa EC70 v4 and EC71 v4 in the local discovery mechanism, which …

CVE-2026-53912

Cerebrate before version 1.37 exposed credential material from self-registration requests. The self-registration workflow stored the registrant’s hashed password in the …

CVE-2026-47177

Quest Bot is an opensource modern Discord Bot built for moderation, utilities and support. Prior to version 1.0.4, a user …

CVE-2025-5266