A phishing site could have repurposed an `about:` dialog to show phishing content with an incorrect origin in the address bar. This vulnerability affects Firefox < 122 and Thunderbird < 115.7.
https://www.mozilla.org/security/advisories/mfsa2024-04/
https://www.mozilla.org/security/advisories/mfsa2024-01/
https://lists.debian.org/debian-lts-announce/2024/01/msg00022.html
https://lists.debian.org/debian-lts-announce/2024/01/msg00015.html