Just a couple hours earlier, PSN and Qriocity sign-in was taken down and it was said that they were under maintenance due to a large amount of password reset email still being undelivered. Just after that Eurogamer and Kotaku reported that it was due to an exploit which allowed hackers to easily change passwords using only PSN account email and Date of Birth of user. It was actually an exploit in the password reset page which many users received in their email.
Sony immediately took down the sign-in services for a couple of its sites including Playstation.com and Playstation forums. The exploit was first discovered on Nyleveia.com and was later reported by NeoGAF users as well. Sony has now officially confirmed this news on the Playstation blog saying that there was no hack involved, it was just a url exploit. The statement reads:
We temporarily took down the PSN and Qriocity password reset page. Contrary to some reports, there was no hack involved. In the process of resetting of passwords there was a URL exploit that we have subsequently fixed.
Consumers who haven’t reset their passwords for PSN are still encouraged to do so directly on their PS3. Otherwise, they can continue to do so via the website as soon as we bring that site back up.
Source: Playstation Blog