Works here, just upgraded to 100 using .tar version.
Clicked on menu, Help, About Firefox and it checked for updates. Showed checking for updates and changed to update to 100. Clicked on it and it downloaded small file and changed to restart to update Firefox. Restarted and now have 100.
Just unsure of automatically, just pushed button and it did automatically upgrade using check for updates vs did not try automatically install updates in settings. Prefer to choose when.
