Computer Help and Support

multiple Firefox instances (can that even be done?) and that hints that your registry is corrupted, and perhaps bogus Firefox instances. FWIW, a wild guess based on no web search, but recollections of past jobs (and malware) Malware always likes to edit the registry to launch multiple versions of itself.

In any event, a thorough check of the system and the registry are always a good idea. However you can do that.

Good luck.
I'll edit/delete if any of this is wrong.