Navigation events were not fully adhering to the W3C's "Navigation-Timing Level 2" draft specification in some instances for the unload event, which restricts access to detailed timing attributes to only be same-origin. This resulted in potential cross-origin information exposure of history through timing side-channel attacks. This vulnerability affects Firefox < 69, Thunderbird < 68.1, Thunderbird < 60.9, Firefox ESR < 60.9, and Firefox ESR < 68.1.
https://www.mozilla.org/security/advisories/mfsa2019-30/
https://www.mozilla.org/security/advisories/mfsa2019-29/
https://www.mozilla.org/security/advisories/mfsa2019-27/
https://www.mozilla.org/security/advisories/mfsa2019-26/
https://www.mozilla.org/security/advisories/mfsa2019-25/
https://w3c.github.io/navigation-timing
https://usn.ubuntu.com/4150-1/
https://security.gentoo.org/glsa/201911-07
https://bugzilla.mozilla.org/show_bug.cgi?id=1560495
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