It seems ESEA, an esports community site dedicated mostly to Counter-Strike, was hacked during December, a breach that apparently allowed access to over 1.5 million user profiles. The hacker responsible reportedly demanded a ransom of $100,000 US dollars from ESEA to prevent leaking or selling the information, a demand the site refused to indulge.
The demand was apparently first reported on December 27, but the hacker finally went through with his threats, leaking the user data online. It seems this data includes usernames, emails, private messages, IPs, mobile phone numbers, forum posts, hashed passwords, hashed secret question answers, and even info related to location.
ESEA has since announced they have patched the security vulnerability, and are now working with the FBI and experts to track down the hacker (or hackers). We'd advise taking care with your account at the moment, though.