Can someone tell me why when I open Mozilla Firefox everything goes to the background and a close button appears? Oh, this is Zorin 17.3 Pro . . .
I see you have sidebars tool enabled and it is showing a blue spot. Have you looked at that?
I on purpose do not use sidebars on Firefox or LibreWolf, So cannot test for you.
Does this happened now or exists this a longer Time? Is Firefox installed as Flatpak or .deb Package?
installed as Flathub
Then I would sugegst to try it with the .deb Package and see if it behaves the same.
thanks, I will and let you know . . .