UPDATE: Speaking to SPOnG about the breach of the PlayStation Store's security, a Sony representative has said:
"to date we can tell you that on a global basis we don't know of a single person who has been affected by this. We take our responsibilities and the protection of consumers' personal information extremely seriously. That is why we are attempting to be transparent in terms of notifying people that we discovered a loophole, which we have now closed. We identified a small number of people who were exposed to the risk of being affected and those we have contacted.”
Sony has stated that unauthorised users may have accessed personal information on PlayStation Store accounts.
An alert on the PlayStation website tells us:
"We have found out that there has been a possibility of unauthorized access to personal information on the PlayStation Store through PCs, a content download service of the PlayStation Network. Although unlikely, it is possible that the passwords of a small percentage of PlayStation Network users may have been changed through unauthorized access, making it possible to view users’ personal information and/or use the Wallet for the PlayStation Store. PlayStation Network accounts do not display entire credit card numbers, so any unauthorized access to your PlayStation Network account is very unlikely to compromise your credit card number."
Sony goes on to state that it has taken measures to address the issue and that security has been restored.
The company is contacting users who may have been affected directly. In the meantime, however, users are advised to log in to their accounts. If you are able to access your account with your pre-set password, Sony says that you have not been affected by the problem.
It has not been confirmed whether users who have had their Wallets used will be reimbursed by Sony.