Wanting to watch some subtitles on a film and not figuring out how it works on VLC, downloaded 'Video + Subtitle DX' from the Windows Store
When I used laptop later, new search screen, new advert tabs opening all over the place, a remote access application trying to install and all sorts.

Windows Defender finally picked up a few of them, Malware Bytes got rid of the rest except for the particularly resistant MyStartSearch which only ADW Cleaner managed to remove.
If Windows Store wants to be a trusted place, like iOS App Store, this sort of stuff should be caught before being approved.