"unknown source" warning when updating Firefox
I have two identical computers running Firefox on Windows 7. No serious issues for 3 years or longer.
Just recently, version 100 showed "Unknown Source" instead of the normal UAC authorization window which lists mozilla.org as the source.
The 100.0.1 update showed the same warning.
This only occurred on one of the computers. The other one does not show the warning.
Firefox worked fine after doing the downloads anyway, but the "Unknown Source" is not right and makes the user think security is being compromised.
Do a clean reinstall of the current Firefox release and delete the Firefox program folder before installing a fresh copy of the current Firefox release.
- download the Firefox installer and save the file to the desktop
If possible uninstall your current Firefox version to cleanup the Windows Registry and settings in security software.
- do NOT remove "personal data" when you uninstall the current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including personal data in profiles created by other Firefox versions
Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.
- (64-bit Firefox) "C:\Program Files\Mozilla Firefox\"
- (32-bit Firefox) "C:\Program Files (x86)\Mozilla Firefox\"
- it is important to delete the Firefox program folder to remove all the files and make sure there are no problems with files that were leftover after uninstalling
Your personal data like bookmarks is stored in the Firefox profile folder, so you won't lose personal data when you reinstall or update Firefox, but make sure NOT to remove personal data when you uninstall Firefox as that will remove all Firefox profile folders and you lose your personal data.
If you keep having problems then you can create a new profile as a quick test to see if your current profile is causing the problem.
I have a third computer which we use just for online banking, also running Firefox.
When I updated to ver 100.0.1, UAC also showed "Unknown Source".
Simultaneous failure of two different computers seems to point to a problem with the Mozilla "publisher's certificate" (or whatever method is used to identify the source to UAC.)
I can uninstall/reinstall Firefox -- the procedure isn't that difficult.
Where are the certificates stored? Can they be refreshed?
For installing Firefox 100.0 version on Windows 7, see this article as it involves installing KB4474419 to support the SHA-256 digest that is used for signing the Firefox 100 installer (SHA-1 is no longer used in Firefox 100).
Beginning in this release, the Firefox installer for Windows is signed with a SHA-256 digest, rather than SHA-1. Update KB4474419 is required for successful installation on a computer running Microsoft Windows 7. For more details about this update, visit the Microsoft Technical Support website.