Thanks for letting me know, it's a bit strange as nothing has actually changed AFAIK, the .NET assemblies have never been signed.
I just tried it on a spare Win7 machine, no warning was shown.
I'm using Win10 so that might make a difference.
I checked that there are no Digital Signatures attached to both 2.90 and 3.01 so that's not it.
I might have disabled the warning for the 2.90 executable before, but I can't remember.
Anyway, I can just disable the warning for CharPadPro301_W64.exe as it's a per file setting.