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.