Liquid loss by the rear of the vehicle

Hello everyone. I have a Ford Focus TDCI of the year 09´. It is 1.6 110cv. The car is usually quite well but recently detected that it left a brown spot on the back. One day I got underneath to see it and found that more or less for the rear bridge has a deposit with connectors and loses from there. I think he just loses when he is hot because he looked already dried. I could not see it well because it is the sedan and I could not get well. Can someone tell me what that is ??? Muxas thanks.