While trying to fix Firefox's massive memory leaks, I went to Help/Troubleshooting/Add-Ons and found these, which are NOT in the usual Manage Add-ons page: Amazon.com extension Bing extension ClearURLs extension <-- Oops! I actually installed this, to try to trim URLs of all the tracking crap when I paste one into a Facebook comment. DuckDuckGo extension eBay extension Wikipedia (en) extension All of the other extensions listed are ones I installed and wish to keep. EVERY time I install Firefox, I go to the One-Click Search Engines list and remove all but Google. I don't know how these wormed their way in, but they don't seem to add any functionality for me.