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.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-43531
• https://bugzilla.mozilla.org/show_bug.cgi?id=1659155
• https://www.mozilla.org/security/advisories/mfsa2021-48/