Firefox, Firefox ESR, and Thunderbird] are vulnerable to Arbitrary Code Injection. The vulnerability is due to the incorrect honoring of Set-Cookie response headers in multipart HTTP responses. If an attacker could manipulate the Content-Type response header and control part of the response body, they could inject Set-Cookie headers that the browser would incorrectly honor.
bugzilla.mozilla.org/show_bug.cgi?id=1864385
lists.debian.org/debian-lts-announce/2024/03/msg00000.html
lists.debian.org/debian-lts-announce/2024/03/msg00001.html
security-tracker.debian.org/tracker/CVE-2024-1551
www.mozilla.org/security/advisories/mfsa2024-05/
www.mozilla.org/security/advisories/mfsa2024-06/
www.mozilla.org/security/advisories/mfsa2024-07/