CVE-2026-100830: Mozilla Firefox

High severity, CVSS 8.1. EPSS: 0.2% chance of exploitation in the next 30 days.

Mitigation bypass in the DOM: Navigation component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.

Affected products

• Mozilla Firefox
• Mozilla Thunderbird

Published 2026-09-29. Last modified 2026-10-01.