Basically, a lot of people's neopets accounts have had the following two changes made:
1) The e-mail attached to their account has been changed in a specific way: by the addition of a string of randomized characters before the @ symbol. (Example:
(you need an account to see links) may become
(you need an account to see links))
2) The passwords of said accounts have been similarly affected, with a string of random characters simply added on to the end. (Shoyru may become Shoyru2g5rif.)
RIGHT NOW, WE ARE NOT CERTAIN THIS IS A SECURITY ISSUE. Several things aren't adding up:
1) Many of the changed e-mails do not actually exist. It is normally impossible to finish changing the e-mail attached to your account if what you type in does not exist, because you have to go to the new e-mail to confirm.
2) No one is reporting anything stolen as of yet.
3) Instead of mostly reasonably-rich accounts being targeted, there appears to be no pattern.
Instead, this may be a particularly scary glitch, or a script-based prank along the lines of the Pant Devil Pages from 2009 (where you would visit a page and suddenly all your NP would be withdrawn) or the random-named grundo creation from a while back (where you would visit a page and a randomly-named green grundo would suddenly be born on your account). If you're using a free internet e-mail provider, then taking the following steps may be helpful:
1) Check and see if your e-mail has been changed. If it has, DO NOT LOG OUT.
2) Go and see if the new e-mail already exists. If not, make it.
3) Send the password retrieval form.
4) Ta-da.
If at any point you can't complete this process, then you'll need to send a ticket. BE FOREWARNED THAT IT'S VERY LIKELY TNT WILL FREEZE YOUR ACCOUNT IF YOU DO THIS in order to protect it from scammer activity. If you don't already keep a hoard of information about your account, now's the time to go get it, because if you are frozen you will need it to get back in. This guide has a list of info you may need to regain access should things go sour.