Hey guys, it wouldn't let me answer the question without asking a question to create an account-- I fixed my problem (when I would open one tab, it automatically opened two...) by clicking an ad down in the bottom left hand corner of the new tab and selecting uninstall. I guess it is a pop-up of some sort that Mozilla automatically downloads. Again: Bottom left hand corner > uninstall. I hope this helps fix you guys' problem as well! :)