Mozilla developers and community members reported memory safety bugs present in Firefox 64 and Firefox ESR 60.4. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code. This vulnerability affects Thunderbird < 60.5, Firefox ESR < 60.5, and Firefox < 65.
https://www.mozilla.org/security/advisories/mfsa2019-03/
https://www.mozilla.org/security/advisories/mfsa2019-02/
https://www.mozilla.org/security/advisories/mfsa2019-01/
https://www.debian.org/security/2019/dsa-4392
https://www.debian.org/security/2019/dsa-4376
https://usn.ubuntu.com/3897-1/
https://usn.ubuntu.com/3874-1/
https://security.gentoo.org/glsa/201904-07
https://security.gentoo.org/glsa/201903-04
https://lists.debian.org/debian-lts-announce/2019/02/msg00024.html
https://lists.debian.org/debian-lts-announce/2019/01/msg00025.html
https://access.redhat.com/errata/RHSA-2019:0270
https://access.redhat.com/errata/RHSA-2019:0269
https://access.redhat.com/errata/RHSA-2019:0219
https://access.redhat.com/errata/RHSA-2019:0218
http://www.securityfocus.com/bid/106781
http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00021.html