CVE-2026-84129

Name of the Vulnerable Software and Affected Versions Firefox versions prior to 155 Firefox ESR versions prior to 153.2 Thunderbird versions prior to 155 Thunderbird versions prior to 153.2

Description A site isolation issue exists within the DOM Navigation component. Site isolation is a security mechanism that ensures web pages from different sites are processed in separate processes to prevent data leakage.

Recommendations Update Firefox to version 155. Update Firefox ESR to version 153.2. Update Thunderbird to version 155. Update Thunderbird to version 153.2.