Deciding which browser extensions are trustworthy has always been an uncertain business. If an add-on is highly rated, with plenty of users, then it should be safe… But as the recent issues over Chrome extensions showed, with popular add-ons being purchased and tweaked to push adverts, there are no guarantees.
Extension Defender is a new service which helps by cataloging malicious Chrome and Firefox extensions. This can be searched manually, but it's probably simpler to install the Chrome or Firefox extension, which can check and protect your system automatically.
Extension Defender's interface is, well, rather basic. It offers two sections, "Scan" and "Options". Click the second, and you’re told "there's currently no options to set". The first has only a "Scan" button and clicking this returns its results in a second or two.
Anything dubious will be listed in a simple report. A "Remove" button uninstalls the extension right away, and a "Rescan" option should confirm your system is clear.
A notification badge on the extension icon also displays the number of malicious extensions you've installed. Signatures are updated automatically, and Extension Defender then detects and allows you to block malicious extensions before they're installed.
We're not yet sure how effective the service will be. The database will need to be expanded (right now it lists 78 Chrome extensions, but only 8 for Firefox), and it remains to be seen how quickly Extension Defender can respond to a new threat. It's lightweight and easy to use, though, so if you regularly try new Chrome extensions then it might be worth a look.