Potentially hacked

Ok I was just writing a support question and my Firefox crashed. So basically my settings are completely unusable as they are EXTREMELY laggy and frozen. I have to close the app and reopen it for my firefox to work. All of this started when a little purple triangle with an exclamation mark appeared next to the three dots in the corner of my screen. It would only appear for a second or so when i opened firefox and it would then disappear. I actually tried checking on mozilla supprot but nothing was found about a "purple" triangle. It started when i accidentally clicked on something and got a fake mccaffe popup that i dismissed. I'm a bit concerned. I need help.