Shamelessly copying Cruor's post:
Y'know how paypal banned Mangatraders and then that one guy donated $1800 in bitcoin to save it? Yeah, it proceeded to get hacked (money wasn't stolen though). MAL, anidb, and Mangaupdates were all hacked afterwords because admins of mangatraders used the same passwords. But from what I get, they actually had pants on and didn't get buttdevastated as well.
Reddit thread link
4chan thread link mentioned in thread
Anyway, if you have a mangatraders account (or see your email in the txt files) and you use the same password errywhere start changing them.