CVE-2022-29916: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.7% chance of exploitation in the next 30 days.

Firefox behaved slightly differently for already known resources when loading CSS resources involving CSS variables. This could have been used to probe the browser history. This vulnerability affects Thunderbird < 91.9, Firefox ESR < 91.9, and Firefox < 100.

Affected products

• Mozilla Firefox: before 100.0 (fixed in 100.0)
• Mozilla Firefox ESR: before 91.9 (fixed in 91.9)
• Mozilla Thunderbird: before 91.9 (fixed in 91.9)

Published 2022-12-22. Last modified 2026-06-17.