Oil loss

Hello, Had recently discovered the car on stage and the following ( see picture) You can see the oil on the oil pan and on the cable, only this place, otherwise everything is dry and clean. I screwed the oil pan and screwed the fixing screw for the cable too. I could not find out, however, where does the oil come out. Is this the oil pan seal or the sensor that is screwed in there. has someone already had such a thing? It is a petrol tanker, R56 Cooper, BJ 2010, 122 HP, running leash ==References==