Japanese and US community portal Square Enix Members has been taken offline after the publisher detected a security breach.
"We have reason to believe that unknown parties may have gained unauthorized access to a particular Square Enix server related to the free Square Enix Members service offered in North America and Japan," the website announced.
"In response, Square Enix, Inc. has temporarily suspended operation of the Square Enix Members service starting at 10PM (PST) on December 12, 2011."
The post advises that Square Enix is still assessing the breach to determine if user data was compromised, but is certain more sensitive information is safe.
"While some personal information may have been accessed, we can confirm that there is no possibility of any credit card information leak from this incident, since the server in question stores no credit card information," the post continued.
"We estimate that the suspension will continue for a few days until we complete our investigation and counter-measures. We will update you as we learn more."
The post ends with an apology and assurance that the publisher takes security "extremely seriously".
Square Enix Members is an optional community which rewarded fans of the publisher's games with prizes and access to exclusive merchandise.