As discovered by Malwarebytes researcher Pieter Arntz, a new pair of extensions plaguing Google's Chrome and Mozilla's Firefox can hijack the browsers in order to push technical support scams at you and potentially even spy on your browsing activities.
Called "Tiempo en colombia en vivo" on the Chrome Web Store, the rogue extension can be installed on a machine when the user visits certain sites; trying to leave a malicious site results in an infinite loop of dialog boxes cautioning the user that they can't leave the page until they install the extension. If they try to leave still, and choose the option to "Prevent this page from creating additional dialogs," the tab will go into full screen mode and offer the 'Add extension' dialog popup that shows up when installing a Chrome extension.
If the user ends up installing the extension, it will proceed by hijacking their browser searches and redirect them to certain pages or YouTube videos in order to increase their views.
Interestingly, the extension is designed to also make its removal a difficult procedure; the first measure taken to ensure this is to redirect users from the 'chrome://extensions/' page where they could manage and delete the extension to 'chrome://apps/?r=extensions', which simply lists the various Chrome apps and extensions that they have installed.
A similar extension for Firefox was also found by the researcher, which is propagated by ad-rotators showing it as a 'manual update for Firefox' and tricking users into installing it. This, too, has similar feature aimed at making its removal more difficult by closing any tab that contains the 'about:addons' string - the page you'd use to manage and delete extensions in Firefox.
However, thankfully, removing the extension in Firefox is much easier than in Chrome, as you only need to start the browser in Safe Mode by pressing down the Shift key when starting it. This will allow Firefox to run with all extensions disabled, and you can then remove the extension as you normally would.
Even though the extension was reported by Arntz to Google privately more than three weeks ago, it was only removed from the Chrome Web Store this Wednesday. You may still be affected by it, however, as Chrome allows sideloading extensions when developer mode is on, and adding the extensions from nefarious sites would allow it to be installed on your PC. Google also removed four malicious extensions that had affected as many as 500,000 users earlier this week.