It's actually a false flag which many devs even put in their descriptions at times. Windows Defender may flag a game on itch.io as a virus when there really isn't anything.
It's due to a false positive from the program's code or a lack of a digital signature.
If you don't trust it that's fine but it is completely okay. Every time a game triggers this it's always Wacatac.B. It's on Microsoft's end.