Same-Origin Policy Bypass in Firefox WebExtensions by Mozilla

CVE-2026-100803

What is CVE-2026-100803?

A vulnerability in the WebExtensions component of Mozilla Firefox has been identified, allowing attackers to bypass the same-origin policy. This issue can potentially lead to unauthorized access to sensitive data across different origins. Mozilla has addressed this vulnerability in multiple versions, including Firefox ESR 153.4, Firefox 157, and several others. Users are advised to update their browsers to maintain security and protect against possible exploits.

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