CVE-2026-100803

Name of the Vulnerable Software and Affected Versions Firefox versions prior to 157 Firefox ESR versions prior to 115.42 Firefox ESR versions prior to 140.17 Firefox ESR versions prior to 153.4 Thunderbird versions prior to 157

Description A same-origin policy bypass exists in the WebExtensions component. The same-origin policy is a critical security mechanism that restricts how a document or script loaded from one origin can interact with a resource from another origin.

Recommendations Update Firefox to version 157 or later. Update Firefox ESR to version 115.42 or later. Update Firefox ESR to version 140.17 or later. Update Firefox ESR to version 153.4 or later. Update Thunderbird to version 157 or later.