firefox is vulnerable to information disclosure. The vulnerability exists by combining the slipstream research combined with a malicious webpage could have exposed both an internal network’s hosts as well as services running on the user’s local machine.
bugzilla.mozilla.org/show_bug.cgi?id=1677940
lists.debian.org/debian-lts-announce/2021/04/msg00019.html
lists.debian.org/debian-lts-announce/2021/04/msg00020.html
security-tracker.debian.org/tracker/CVE-2021-23961
security.gentoo.org/glsa/202104-09
security.gentoo.org/glsa/202104-10
www.debian.org/security/2021/dsa-4895
www.debian.org/security/2021/dsa-4897
www.mozilla.org/security/advisories/mfsa2021-03/