Bills made with Photoshop are a huge threat. They are just everywhere...

I hate that Adobe went the cloud way. On the other hand Gimp, Krita, Blender are better than ever and in my opinion can compete without problem.

Krita is a phenomenal piece of software. It's very bulky but ever since I switched from gimp, there's no looking back.

I wonder what software the graphic designers who design new bills use?

Illustrator. I'd be surprised if bank notes aren't in a vector format

Having worked for government, I wouldn't be surprised if it was done by graphic design student who got the job cause they knew someone and they don't even know what a vector is.