CVE-2025-5263: Mozilla Firefox

Medium severity, CVSS 4.3. EPSS: 0.2% chance of exploitation in the next 30 days.

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 (fixed in 115.24.0); before 139.0 (fixed in 139.0); from 116.0, before 128.11.0 (fixed in 128.11.0)

Published 2025-05-27. Last modified 2026-10-05.