I was reading another question which mentions a site that had a page inviting people to try to hack it, and it made me wonder.

Lets assume, for the sake of this rather hypothetical question, that a site has a page asking people to hack it, and that the page did not specify which kind of hacking was or wasn't acceptable.

Does placing such a page provide a legally/ethically sufficient indication that this site is really expecting to be hacked? Are there any legal/contractual/ethical requirements to be set before publishing or executing those kind of challenges?

Does it really mean all bets are off and any kind of attack is acceptable?