In order to prevent future errors caused by the SSL scanning feature of many antivirus programs, Mozilla is performing a test that imports the Windows root certificates into Firefox. This allows Mozilla to retain full control over what certificates will be trusted when browsing the web. The test is being pushed out to users of Windows 10 and Windows 8 who have an antivirus program registered other than Windows defender and do not have the security.enterprise_roots.enabled flag enabled already. If this test does not cause other issues to arise, we should expect to see this configuration setting enabled by default going forward.
Source: https://www.bleepingcomputer.com/news/software/firefox-to-import-windows-root-certs-to-avoid-antivirus-ssl-scanning-issues/