[JupiterMoon]

They just flash a dialogue up with an opt out button. Closing the dialogue is consent to go ahead with the update. Most people close those kind of annoying pop ups without reading the message. So technically MS aren't push a mandatory update - de-facto to millions of people they are though.

[PretzelFisch]

They pop up an information dlg telling you it will be upgraded. clicking x like close does nothing as it should. The lesson to learn is to not enable os auto updates, anywhere.