CVE-2026-16387

A critical site isolation vulnerability in the Networking component of Firefox and Thunderbird could allow attackers to bypass security boundaries, potentially leading to data leakage or unauthorized access to sensitive information. Users of affected versions should prioritize updates to Firefox 153, Firefox ESR 140.13, Thunderbird 153, or Thunderbird 140.13 to mitigate the risk. Organizations relying on these applications for secure communications must act swiftly to protect their systems.