This is an alarm that you need to check every single switch and receptacle in your house.
Ground and neutral are bonded together at your main panel. That's the only place they're supposed to be bonded. But, consequently, ground wires are viable return paths for the hot circuit.
In this case the ground wire appears to have been connected instead of the neutral wire. This is incredibly dangerous not only because it's an uninsulated (and possibly smaller) wire but because it's presumably connected to every metal fixture and appliance in your home. The receptacle will still be functional because electricity can flow just fine along the ground wire.
It is a fire hazard. It is a kill you if you touch the wrong thing hazard. It is a "whoever did this was so absurdly wrong that I trust nothing" hazard
Now, all those hyperboles aside. As long as you don't plug anything into that receptacle nothing is likely to go crazy wrong. Do not use it. But I'd be more concerned about the receptacles you are using.
If I discovered this in my own home I would immediately make arrangements to inspect every electrical device. Call an electrician to handle it if you have any ambiguity.