Mozilla developers reported memory safety bugs present in Firefox 71 and Firefox ESR 68.3. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox ESR < 68.4 and Firefox < 72.
https://www.mozilla.org/security/advisories/mfsa2020-02/
https://www.mozilla.org/security/advisories/mfsa2020-01/
https://www.debian.org/security/2020/dsa-4603
https://www.debian.org/security/2020/dsa-4600
https://usn.ubuntu.com/4335-1/
https://usn.ubuntu.com/4241-1/
https://usn.ubuntu.com/4234-1/
https://security.gentoo.org/glsa/202003-02
https://seclists.org/bugtraq/2020/Jan/26
https://seclists.org/bugtraq/2020/Jan/18
https://seclists.org/bugtraq/2020/Jan/12
https://lists.debian.org/debian-lts-announce/2020/01/msg00016.html
https://lists.debian.org/debian-lts-announce/2020/01/msg00005.html
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1507180%2C1595470%2C1598605%2C1601826
https://access.redhat.com/errata/RHSA-2020:0295
https://access.redhat.com/errata/RHSA-2020:0292
https://access.redhat.com/errata/RHSA-2020:0127
https://access.redhat.com/errata/RHSA-2020:0123
https://access.redhat.com/errata/RHSA-2020:0120
https://access.redhat.com/errata/RHSA-2020:0111
https://access.redhat.com/errata/RHSA-2020:0086
https://access.redhat.com/errata/RHSA-2020:0085
http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00043.html
http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00029.html