Remember those times when you used Internet Explorer 5 or 6 and you used Google's toolbar to search the web? You could have installed it yourself, or it came bundled with another program and you missed an important tick mark during installation. Those unwanted toolbars still exist and Google has decided to put a hold on those silent installs.
Starting with Google Chrome 25, programs can no longer silently install extensions without your permission. They will be disabled by default, however Chrome will tell you when it detects a new extension you didn't install yourself by displaying a badge on the menu button. Then you can click through the menu to enable or remove the new extension.
