An improper implementation of the new iframe sandbox keyword <code>allow-top-navigation-by-user-activation</code> could lead to script execution without <code>allow-scripts</code> being present. This vulnerability affects Thunderbird < 91.9, Firefox ESR < 91.9, and Firefox < 100.
https://bugzilla.mozilla.org/show_bug.cgi?id=1761981
https://www.mozilla.org/security/advisories/mfsa2022-16/