Net Security said:Google has instituted a new rule that should keep Chrome users safe from malicious add-ons: starting with version 21.0.1180.41 (currently in beta), the browser will block all third-party extensions, apps, and user scripts that are not hosted on the Chrome Web Store.
The move is aimed at preventing the all-too-popular attacks mounted through booby-trapped websites that automatically trigger the installation of malicious extensions. These extensions often keep tabs on what pages the user is visiting.
Google is looking to check all third-party extensions that are submitted to the Chrome Web Store for signs of malicious functionality.
Read more: https://www.net-security.org/secworld.php?id=13258