Web-accessible extension pages (pages with a moz-extension:// scheme) were not correctly enforcing the frame-ancestors directive when it was used in the Web Extension's Content Security Policy. This vulnerability affects Firefox < 97, Thunderbird < 91.6, and Firefox ESR < 91.6.
https://www.mozilla.org/security/advisories/mfsa2022-06/
https://www.mozilla.org/security/advisories/mfsa2022-05/