Mozilla developers and community members reported memory safety bugs present in Firefox 67. 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 Firefox < 68.
https://www.mozilla.org/security/advisories/mfsa2019-21/
https://security.gentoo.org/glsa/201908-12
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00017.html
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00011.html
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00010.html
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00009.html