Re: "no browser extensions should be allowed to install automatically"
Absolutely. Have we not been here before? Many, mamy times, and many moons ago, with things with shitty IE plugins that trash your online life?
Speaking as an IT admin that loves it when silent installs are possible, they are also simply disasterous for home users with vendors and the likes pushing what they think is best into other people's systems. If your users can't be persuaded to click a "Yes" box by your shitware, then perhaps fix your shitware.