From that photo alone, that looks like someone didn’t want to deal with changing the outlets when they painted the walls and that’s just paint warn off of a dark brown receptacle from many years of plugs being inserted.
As one who has done many dumb things in my life, evidence of small electrical fires would be whispy smokey gray possibly with some meltiness.
Side note, autocorrect tried to make “dumb” be “fun” and I couldn’t feel more seen right now.
Ok