I also got this setup dialog after I did a Windows update last night, and I also clicked on "Don't update your browser settings". Just went back and checked - my default browser is still set to Firefox, and .html files are still configured to open with Firefox. So it's possible that the poster encountered some bug specific to his configuration rather than a malicious browser hijacking campaign by Microsoft. (I'm runn…
It may not be universal, but it is hardly unique: https://twitter.com/Schouten_B/status/1459952197517684747?s=...