CVE-2025-5263: Error handling for script execution was incorrectly isolated from web content

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-346

Description

Error handling for script execution was incorrectly isolated from web content, which could have allowed cross-origin leak attacks. This vulnerability was fixed in Firefox 139, Firefox ESR 115.24, Firefox ESR 128.11, Thunderbird 139, and Thunderbird 128.11.

Affected products

Mozilla Firefox: before 115.24.0; before 139.0; from 116.0 before 128.11.0 — fixed in 115.24.0, 128.11.0, 139.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 115.24.0, 128.11.0, 139.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1960745
https://www.mozilla.org/security/advisories/mfsa2025-42/
https://www.mozilla.org/security/advisories/mfsa2025-43/
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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