Is this a serious threat
firstname.lastname@example.org].arena Extension Virus is your regular dubious browser plug-in to add to the already huge list of identical contaminations. Users for the most part get invaded when they incorrectly set up free applications, and what they do is they hijack browsers and alter their settings. Expect to get redirected to strange sites and do not be shocked if you encounter more advertisements than usual. It will not bring anything useful to you as it aims to simply generate revenue.