CVE-2021-43540: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 0.9% chance of exploitation in the next 30 days.

WebExtensions with the correct permissions were able to create and install ServiceWorkers for third-party websites that would not have been uninstalled with the extension. This vulnerability affects Firefox < 95.

Affected products

• Mozilla Firefox: before 95.0 (fixed in 95.0)

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