If there was a PAC URL set and the server that hosts the PAC was not reachable, OCSP requests would have been blocked, resulting in incorrect error pages being shown. This vulnerability affects Firefox < 102, Firefox ESR < 91.11, Thunderbird < 102, and Thunderbird < 91.11.
https://bugzilla.mozilla.org/show_bug.cgi?id=1770123
https://www.mozilla.org/security/advisories/mfsa2022-24/