Websteroids Extension

Someone please help me, I somehow downloaded an extension to google chrome called websteroids, I have tried deleting it but it justs reinstalls and is hard to find, could someone please help me? I’ve resorted to uninstalling google chrome and I am using firefox at the moment, I would really like to get the extension off of my system, can someone please help?

follow instructions and attach Malwarebytes / OTL logs. http://forum.avast.com/index.php?topic=53253.0