CVE-2026-53900: Mozilla Firefox Mobile

Medium severity, CVSS 4.3. EPSS: 0.1% chance of exploitation in the next 30 days.

Firefox for iOS preserved cookies set on the initial PDF request across cross-origin HTTP redirects in TemporaryDocument, allowing a malicious site to inject arbitrary cookies into requests to an unrelated target domain. This vulnerability was fixed in Firefox for iOS 152.0.

Affected products

• Mozilla Firefox Mobile: before 152.0 (fixed in 152.0)

Published 2026-06-16. Last modified 2026-06-17.