The personal information of up to 20 million users on a Russian dating site could be at-risk after their email addresses and usernames were stolen and put up for sale online.

Easy Solutions, a fraud-detection software provider, discovered the breach after seeing a post on an online forum by a user named “Mastermind,” according to Bloomberg News. The affected site, Topface, has more than 90 million users. Most access their accounts through Facebook or other social media networks.

Half of the stolen credentials came from Russia, and 40 percent came from the European Union. Approximately 7 million users used Hotmail.com; 2.5 million users used Yahoo.com, and 2.3 million used Gmail.com.

The stolen data could be used to try to access bank accounts, health records and other sensitive information, Bloomberg reported.