Well, the statement implies that Mt.Gox is down because it was "compromised", as far as I understand it is actually under DDoS attack ... if it's "compromised" what is the need for a DDoS to take it down? I don't know ... by whatever the case, it seems "Buttsec" doesn't have evil intentions

"ButtSec
Oh hai. We've gained access to some Bitcoin exchange sites. Obviously this includes Mt Gox, which is currently down. Hm wonder why?
Here at Buttsec we're fans of Bitcoin, but we must get the message out there that security is sorely lacking on many of the exchange sites! We will speak with some of these sites in the coming days. If your users aren't given answers, expect some information to make it to the public! ;-)
Yours truly, Buttsec
Bitcoin donations: 15gvHsFAq5RQaFSzUFQUCTCqAjrVoMjv2P
Twitter: @buttsecurity"