Some leaks can from accidental statements by actors, or the like. I'm not talking about that.
I'm think of blackhat leaks, which can be illegal.
Do we allow such leaks on the site?
The Stack Exchange Terms of Service expressly forbid using the service for illegal activity. These two sentences seem particularly relevant:
Any fraudulent, abusive, or otherwise illegal activity or any use of the Services or Content in violation of this Agreement may be grounds for termination of Subscriber’s right to Services or to access the Network. [...]
Use of the Network or Services to violate the security of any computer network, crack passwords or security encryption codes, transfer or store illegal material including that are deemed threatening or obscene, or engage in any kind of illegal activity is expressly prohibited.
I imagine reposting material that was obtaining illegally falls squarely under that second sentence. Don't do it.
If you see illegal material, then please edit to remove it. If the OP has a pattern of posting illegal content, or it should be obvious that it was illegal, then flag for moderator attention with the custom flag reason. Explain why you think the content was obtained illegally – they can decide what to do next, and escalate it to SE Staff as necessary.
ETA, after 12 hours reflection: When I wrote the hard-lined response above, I was thinking in very black-and-white terms. I am not a lawyer. The OP’s use of the word “blackhat” made me think of things that any reasonable person would find nefarious or illegal.
For example: there’s a grey area (that we tend to let slide) with respect to quoting scripts for released films that are posted online, even though they probably aren’t there with the writer’s permission. But there’s a difference between that and, say, hacking into Joss Whedon’s voicemail to get the latest Avengers rumours.
I am not a lawyer. Legal stuff is hard.