A windows update includes some additional functionality for third party browsers (firefox, opera etc) which may inhibit the ability for bogus / dodgy sites to download software onto the clients computer.
I wonder to what extent this is being blown out of proportion? Adding this .net function to a web browser is designed solely for web-apps to do live updates if they are using the Firefox client.
In another, less techie matter, it shows as much for Microsoft as it does for Mozilla. How well made...