Since nobody else has answered, I'll take a stab at this. I see two Safari plists in ~/Library/Preferences. One is named com.apple.Safari.plist and the other is com.apple.Safari.RSS.plist. Move one of them to the desktop and then log out/in. If the problem is solved, reset the appropriate preferences and trash the plist. If not, put it back and try the other one.*

If the above suggestions are unsuccessful, you can play with the contents of ~/Library/Application Support/Firefox in a similar manner.

*Actually, here's something else that you could try first: Play with com.apple.loginitems.plist and com.apple.loginwindow.plist. Both are located in ~/Library/Preferences.


Jon

macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365