This sort of thing never happened to me, but a friend of mine recently told me how he used to run a forum that was kind of popular. But one day he found out that one of the users was able to access all the backend data somehow. That included usernames, emails. It didn't include the passwords or anything like that though. Well users started to leave and then one of the people who got in hijacked the site and leaked everything, including user messages.
Has anything like this happened?
Has anything like this happened?