dig some dirt up
To uncover negative information about someone or something. Once I contact my usual sources at the tabloids, I should be able to dig some dirt up on that actress.
dig some dirt up (on someone)
Fig. to find out something bad about someone. If you don't stop trying to dig some dirt up on me, I'll get a lawyer and sue you. The citizens' group dug up some dirt on the mayor and used it against her at election time.