An attacker could have created a malicious link using bidirectional characters to spoof the location in the address bar when visited. This vulnerability affects Firefox < 117, Firefox ESR < 115.4, and Thunderbird < 115.4.1.
https://www.mozilla.org/security/advisories/mfsa2023-47/
https://www.mozilla.org/security/advisories/mfsa2023-46/
https://www.mozilla.org/security/advisories/mfsa2023-34/
https://www.debian.org/security/2023/dsa-5538
https://www.debian.org/security/2023/dsa-5535
https://lists.debian.org/debian-lts-announce/2023/10/msg00042.html
https://lists.debian.org/debian-lts-announce/2023/10/msg00037.html