Google announced earlier this week that they are going to end the extensions that are silently added to the browser. When Chrome 25 is launched, external extension deployment options on Windows will be disabled by default and all of the extensions that were previously installed will be automatically disabled. You will still have the option to “Enable extension.”
If you are not sure how an extension got there, you can click on “Remove from Chrome.” Chrome will show you a list of extensions that it is disabling. If you want to keep them, you can click on Extension Settings.
The way that some extensions are able to trick Chrome into installing extensions without permission is by using the Windows registry to enable certain extensions grouped together. This feature was intended for developers to include a Chrome extension as part of an installation of their other software.
After Chrome 25 is released, extensions will no longer be able to be installed without the user’s knowledge. Google is encouraging Windows application developers to install Chrome extensions within the browser.
[Source: TNW/Google Chrome Blog]