Why is there an oily substance on the connector in my circuit breaker?
Sometime a dielectric grease is applied to the connections of a circuit breakers when they are installed, and it can appear to be dripping from the wires..

diy.stackexchange.com/questions/146945/…
Courtesy of Ed Beal And Isherwood


If this is it, leave it in place and don't worry it is supposed to be there.