CVE-2021-23957: Mozilla Firefox

High severity, CVSS 7.4. EPSS: 0.8% chance of exploitation in the next 30 days.

Navigations through the Android-specific `intent` URL scheme could have been misused to escape iframe sandbox. Note: This issue only affected Firefox for Android. Other operating systems are unaffected. This vulnerability affects Firefox < 85.

Affected products

• Mozilla Firefox: before 85.0 (fixed in 85.0)

Published 2021-02-26. Last modified 2026-06-17.