CVE-2021-43531: Mozilla Firefox

Medium severity, CVSS 4.3. EPSS: 0.3% chance of exploitation in the next 30 days.

When a user loaded a Web Extensions context menu, the Web Extension could access the post-redirect URL of the element clicked. If the Web Extension lacked the WebRequest permission for the hosts involved in the redirect, this would be a same-origin-violation leaking data the Web Extension should have access to. This was fixed to provide the pre-redirect URL. This is related to CVE-2021-43532 but in the context of Web Extensions. This vulnerability affects Firefox < 94.

Affected products

• Mozilla Firefox: before 94.0 (fixed in 94.0)

Published 2021-12-08. Last modified 2026-06-17.