A vulnerability exists in the Windows sandbox where an uninitialized value in memory can be leaked to a renderer from a broker when making a call to access an otherwise unavailable file. This results in the potential leaking of information stored at that memory location. *Note: this issue only occurs on Windows. Other operating systems are unaffected.*. This vulnerability affects Thunderbird < 60.7, Firefox < 67, and Firefox ESR < 60.7.
https://www.mozilla.org/security/advisories/mfsa2019-15/
https://www.mozilla.org/security/advisories/mfsa2019-14/