Sure looks familiar. Bad connection resulting in high resistance either in the receptacle, between plug and receptacle or even inside the plug, transferring enough heat to the prong and surrounding receptacle to scorch it like this. Curious thing BOTH holes are equally burnt though, usually it's just one. Old rewireable plugs of high-power appliances often look like this when somebody didn't tighten the screws properly. (particularly remember an ancient 2000W 220V space heater with a Schuko plug looking similar to this receptacle... or the power strip my mom once had under the kitchen sink to plug in the small under sink hot water tank... got wet and that's what it looked afterwards).
