Firefox "blip"

I was surfing a website and then went back to my yahoo homepage. In the upper right hand corner of the browser screen, I saw a black box roughly this size:

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I have no idea what it is. I did a search and found hits for "favicon hijacks," but I am running noscript in the browser. I am still not sure what's happening.

 

Anyone? I am afraid to do any "mission critical" stuff right now.

 

What site are you visiting? Maybe a screen print will help.

 

I was visiting the "real clear politics" website and the Des Moines Register website with NoScript in Firefox 2.0.0.11, and then I went to my Yahoo homepage. I can't reproduce it - it just appeared for about 5 seconds and went away.

 

If I got infected with malware, I know it would have gotten past both the Comodo HIPS and AVIRA, so I ran a-squared. It found two files (HP Games) otto.exe and Lemonade2.exe infected with Backdoor.Win32.Wootbot.gen and Backdoor.Win32.Rbot.aeu respectively.

However, it is most likely a false positive because virustotal came up as completely clean for the first file, but Previx came up as "Heuristic: Suspicious File With Outbound Communications" but the Prevx website says it has no unsafe "tendencies."