I have two user accounts on my Mac which is running OS 10.13.6 High Sierra. I downloaded an update yesterday and now Firefox will not open any web page in one of the user accounts (1st account). I tried clearing the cache and cookies, disabling extensions, disabling plug-ins, starting in Safe Mode and nothing worked. It doesn't open any web page in Safe Mode. So I reinstalled Firefox, and the same exact thing; won't even open web pages in Safe Mode. The other use account (2nd account) works fine. When I reinstalled Firefox I lost all the bookmarks and saved logins in the 1st user account. But the 2nd user account everything is fine. So I'm thinking I may have a corrupt plist file or something like that in the first user account. I can restore from a backup, but I have no idea which files to restore. Help?