CVE-2021-43531

4.3 mediumEPSS 0.3%

Medium (4.3) in mozilla firefox. 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.

Severity

CVSS 3.1

4.3 medium

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

EPSS: 0.3% chance of exploitation in the next 30 days; higher than 27% of CVEs (scores of 2026-10-31)
CWE: CWE-346
Published: 2021-12-08
Modified: 2026-06-17
Record from: the NVD, synced 2026-10-19

Affected

mozilla:firefox

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1659155
https://www.mozilla.org/security/advisories/mfsa2021-48/
https://bugzilla.mozilla.org/show_bug.cgi?id=1659155
https://www.mozilla.org/security/advisories/mfsa2021-48/

Check your stack JSON