I have noticed since 0.62 has dropped that if I Alt/Tab out of the game and then come back to it, if I am holding a gun in my hand it will shoot automatically. If I am not holding a gun, I will punch repeatedly. It will not stop until I press action to punch/shoot and space bar to put my hands away.
This happens every single time I go off the main game screen and come back.
It doesn't happen if I use the steam overlay