CVE-2025-10531: Mozilla Firefox

Medium severity, CVSS 5.4. EPSS: 0.3% chance of exploitation in the next 30 days.

Mitigation bypass in the Web Compatibility: Tooling component. This vulnerability was fixed in Firefox 143 and Thunderbird 143.

Affected products

• Mozilla Firefox: before 143.0 (fixed in 143.0)
• Mozilla Thunderbird: before 143.0 (fixed in 143.0)

Published 2025-09-16. Last modified 2026-06-17.