Posting in the Warhammer Online forums, Brules opens a thread which sums up the situation clearly.
My account I pay my sub from was billed today for over 500 dollars in 16 dollar increments. the account was overdrawn and with fees and overbilling it was 562.73 total.
Andy Belford, the community coordinator for mythic entertainment who manage the game was able to quickly reassure players the payment problem was not due to a hacking.
The team responsible for the security of the Mythic Account Center has investigated the matter and has concluded that we have not been compromised and all of your private/personal information is safe and secure on our end.
As James and I have previously stated, please take your account security very seriously. We advocate the use of all of the above tips for maintaining a secure password and encourage you to practice safe account management. If at anytime you feel as though your account has been compromised please file an in game appeal immediately so that it may be investigated by the Customer Service team.
The problem was actually due to the system sending many billing requests when it should have sent one.
One of Kotaku‘s readers even sent in a screen shot of their bank account.