Then, another tab would open up automatically each time I opened firefox a tab would open offering to update my browser with the path "*.src-click-download.xyz/ + string of characters". The asterisk is there because each time, that part of the url would be different.
I boot-time scanned my computer with avast, which finally removed what I thought had been the source of the problem (yahoo! powered), but the problem persisted. I then used adwcleaner, which stopped that page from appearing every time I open it.
However, firefox still opens a new slot in the task bar, which indicates to me that the root of the problem is still there. I'm all out of ideas, so I was hoping you guys could help me with this.