The updated packages fix security vulnerabilities:
Use-after-free while running the nsDocShell destructor. (CVE-2020-6819)
Use-after-free when handling a ReadableStream. (CVE-2020-6820)
Uninitialized memory could be read when using the WebGL copyTexSubImage method. (CVE-2020-6821)
Out of bounds write in GMPDecodeData when processing large images. (CVE-2020-6822)
Memory safety bugs fixed in Thunderbird 68.7.0. (CVE-2020-6825)