CVE-2026-9309: Mozilla Firefox

Medium severity, CVSS 5.4. EPSS: 0.3% chance of exploitation in the next 30 days.

Firefox for iOS Reader View did not properly escape HTML tags in JSON-LD metadata. A malicious page could inject markup that changed Reader View behavior and leaked sensitive URL parameters. These parameters could then be used to access internal pages, potentially resulting in arbitrary JavaScript execution in an internal origin. This vulnerability was fixed in Firefox for iOS 151.2.

Affected products

• Mozilla Firefox: before 151.2 (fixed in 151.2)

Published 2026-06-01. Last modified 2026-07-22.