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.
https://www.mozilla.org/security/advisories/mfsa2020-08/
https://bugzilla.mozilla.org/show_bug.cgi?id=1420296
Source: Mitre, NVD
Published: 2020-03-25
Updated: 2021-07-21
Base Score: 5
Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:N/A:N
Severity: Medium
Base Score: 7.5
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Severity: High