Firefox opens new tabs

Randomly, a new tab will open up in my browser (firefox), one time it went to under-search.com most of the time, the browser say that that connection to the new tab (the malware, related tab), doesn't connect. Can anyone help with this? Thanks


Quick Update, this might help.

I just tried to go to theshizz.org/forum, and a new random tab opened with this url

This happens alot.

Hi wozz

Click here to download HJTInstall.exe

• Save HJTInstall.exe to your desktop.
• Doubleclick on the HJTInstall.exe icon on your desktop.
• By default it will install to C:\Program Files\Trend Micro\HijackThis .
• Click on Install.
• It will create a HijackThis icon on the desktop.
• Once installed, it will launch Hijackthis.
• Click on the Do a system scan and save a logfile button. It will scan and the log should open in notepad.
• Click on "Edit > Select All" then click on "Edit > Copy" to copy the entire contents of the log.
• Come back here to this thread and Paste the log in your next reply.
• DO NOT use the AnalyseThis button, its findings are dangerous if misinterpreted.
• DO NOT have Hijackthis fix anything yet. Most of what it finds will be harmless or even required.

lack of Response