Outlet with burn marks

What would cause burn marks around an outlet; the outlet checks out ok with the tester? The main panel checks out ok, no burn marks on breakers or wires and is grounded, any ideas?

Whatever was plugged into it shorted out.
Test and observe, then move on.
That simple.

Document it. Burnt electrical receptacle - reason unknown. I recommend replacement when it is not in the original condition in which it was sold.

Thanks for your help. This is a home that my nephew is buying and the home is 19 years old and I had told him that it may be a lose wire or he may need to replace the 3 outlets. Thanks again!

Phil,if the lose wire was in the wall ,it most likely would also have scorches on the sides, but you could have just opened the plate to check.

Phil, Without pics I can’t really tell. But the plug it type transformers for portable phones etc can get hot. I have seen sooo many times that the outlet plate, usually plastic with get blackened. And twice I have been called in to check an outlet because the transformer caught on fire. I would check the wires and replace the outlet. If you go around your own home and feel these transformers, some of them will be warm or hot. Bad, Bad, Bad manufacturer of some of these devices and they are UL rated. But I don’t know if this is your case. Rick