it just on white part sprank plugs and the tip. The reason I chance them cuz my car was jerk on me when i have in drive. I'm at stop just move than shut down on me have start the car up again.
If the black deposit was more dusty than liquid you can just keep an eye on it in the near future.
If the oil was actually wet you may have a broken ring on the piston letting oil enter the combustion chamber (where the spark plug is). If this is the case, you need to get into a shop immediately.