What’s Vulnerable › Vulnerabilities

CVE-2025-5266: Script element events leaked cross-origin resource status

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-05-27 · updated 2026-10-05
• Weakness: CWE-200

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.

Affected products

• Mozilla Firefox: before 128.11.0; before 139.0 — fixed in 128.11.0, 139.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 128.11.0, 139.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1965628
• https://www.mozilla.org/security/advisories/mfsa2025-42/
• https://www.mozilla.org/security/advisories/mfsa2025-44/
• 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

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