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,FirefoxESR<60.9,andFirefoxESR<68.1.