On 32-bit versions there were integer-overflows that led to an out-of-bounds-read that potentially could be triggered by a malformed OpenType font. This vulnerability affects Firefox < 125, Firefox ESR < 115.10, and Thunderbird < 115.10.
https://www.mozilla.org/security/advisories/mfsa2024-20/
https://www.mozilla.org/security/advisories/mfsa2024-19/
https://www.mozilla.org/security/advisories/mfsa2024-18/
https://lists.debian.org/debian-lts-announce/2024/04/msg00013.html
https://lists.debian.org/debian-lts-announce/2024/04/msg00012.html