CVE-2025-10529: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.3% chance of exploitation in the next 30 days.

Same-origin policy bypass in the Layout component. This vulnerability was fixed in Firefox 143, Firefox ESR 140.3, Thunderbird 143, and Thunderbird 140.3.

Affected products

• Mozilla Firefox: before 140.3.0 (fixed in 140.3.0); 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.