From the phpBB FAQ page (phpBB is where our board code comes from):
- According to viewonline a user is doing/reading something they should not be able to!
No, they probably are not. phpBB uses sessions to keep track of users as they move between pages. The session information tells us who this user is. Therefore in order to determine what a user can do on a page we first need the session details. Once this data is available we can check whether the user is permitted to do whatever it is they are trying to do. This can result in it appearing as if a user is reading a topic in a forum they should not be able to access. Or perhaps viewing private messages when they are only guests, etc. In practice the user is not doing these things, they are viewing a "You are not permitted to do this" type message. The session data has simply been updated before we were able to determine what the user could or could not do.