To download Firefox, you need to go to http://www.mozilla.org . That's where you're supposed to go. If you go anywhere else, it's at your own risk, as you've seen. I see they have it here at CNET as well, and I've never had a problem with anything I've downloaded from CNET.
When downloading any applications for installation always be careful. Looking to re-install FIREFOX I ran a search. mozilla-firefox.ez-download.com/ looked like a legit source URL. My Norton even indicated it was OK. After the download a malware scanner I had running indicated it contained TROJAN.W32.Mal.Gen.43923 and disabled the file! A closer look at the hit list turned up at least four bogus file sources. The real one was way down the list. I was in the process of cleaning up after "search.us.com" had stolen my browser home pages. I could not clean up FIREFOX so I de-installed it. I almost installed a worse problem. It's getting harder and harder to get what you really search for with all the search engine corruption going on.

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