Source or example of malicious stuff done?
Things like this[1] should not be possible.
Then you have the black screen with the circle, and then the blue screens "we are configuring your updates and didn't touch your files".
It drives me insane.
In their defense, there was a pretty large subculture of technically knows-enough-to-be-dangerous people who would do everything in their power to totally disable Windows Update for various reasons.
Microsoft looked at this as compromising Windows' security and harming Microsoft's reputation. Their solution in Windows 10 was to make it much more difficult or impossible to delay or turn off updates for Home and Pro users. It's annoying as all hell for those who know what we're doing and do stay up to date. I hate it because it restarts in the middle of the night, then boots up into the Bitlocker screen - so when I get up in the morning I discover my desktop has been running at 100% CPU and blasting fans like a jet engine for god knows how many hours thanks to Windows update.
But at the same time, I can see why they did it, but there had to be a better way.
By itself this isn't horrible, but it (and many other Windows features, for that matter) crosses into malware territory when it treats the user as hostile (like re-enabling itself or working around blocks like DNS)