I'm not sure if this is unintentional or not, and I disabled Steam controller support for my Xbox controller. But still, while the Steam client is running and I'm depressing both thumb stick buttons of my Xbox controller at the same time, I can move the mouse cursor with the right thumb stick. This seems unintentional and feels like some logic is broken in the Steam uinput daemon.

I'm even able to generate other input, like mouse clicks etc. It doesn't seem right.