CVE-2021-29958: Mozilla Firefox

Medium severity, CVSS 4.3. EPSS: 0.7% chance of exploitation in the next 30 days.

When a download was initiated, the client did not check whether it was in normal or private browsing mode, which led to private mode cookies being shared in normal browsing mode. This vulnerability affects Firefox for iOS < 34.

Affected products

• Mozilla Firefox: before 34.0 (fixed in 34.0)

Published 2021-06-24. Last modified 2026-06-17.