CVE-2020-6809: Mozilla Firefox

High severity, CVSS 7.5. EPSS: 1.5% chance of exploitation in the next 30 days.

When a Web Extension had the all-urls permission and made a fetch request with a mode set to 'same-origin', it was possible for the Web Extension to read local files. This vulnerability affects Firefox < 74.

Affected products

• Mozilla Firefox: before 74.0 (fixed in 74.0)

Published 2020-03-25. Last modified 2026-06-17.