I just wanted to point out that since version 65 Firefox creates the folder "%ALLUSERSPROFILE%\Mozilla" (%systemdrive%\ProgramData\Mozilla\updates\...) - the launcher doesn't remove it.
I tried editing the source by adding (don't do this at home - it's only for me and the hard way!):
RMDir /r "%ALLUSERSPROFILE%\Mozilla\"
and elevating the privilegies via 'RequestExecutionLevel admin' - the script compiles without errors but the folder remains there after closing...
I'm sure you'll fix it - happy to see Firefox beeing "clean" again