De Continuando a proteger os usuários do Chrome contra extensões maliciosas :
We’re always working to improve Chrome extensions while keeping our users as safe as possible. In May 2014 we announced a new policy to protect Windows users by enforcing that extensions be hosted on the Chrome Web Store. The results were encouraging: we saw a 75% drop in customer support help requests for uninstalling unwanted extensions. Consequently, we will expand the reach of this protection to all Windows and Mac users in the coming months.
We originally did not enforce this policy on the Windows developer channel in order to allow developers to opt out. Unfortunately, we’ve since observed malicious software forcing users into the developer channel in order to install unwanted off-store extensions. Affected users are left with malicious extensions running on a Chrome channel they did not choose. As such, starting today we will begin enforcing this policy on all Windows channels. Mac will soon follow, with enforcement for all channels beginning in July 2015.
No entanto, conforme descrito em instalações por meio da política corporativa , você tem várias opções que ainda podem ser usadas para sideload .
A mais fácil parece ser usar a política ExtensionInstallForcelist .