Ashley Madison, a dating website targeting married people who want to cheat on their spouses, was breached by hackers, exposing the information of millions of its customers, site owner Avid Life Media confirmed.

In a statement released on Monday, Avid Life Media says they were flagged on an unauthorized attempt by an outsider trying to gain access to their systems. The sites have since been secured.

"We are working with law enforcement agencies, which are investigating this criminal act," the company announced. "Any and all parties responsible for this act of cyber-terrorism will be held responsible."

Avid has not made a comment about the nature of the data that was compromised, but it apparently it includes "user databases, financial information and other proprietary information," according to the blog KrebsonSecurity.

The release by the hacker or group of hackers, self-identified as the "Impact Team," also includes data from two other sites owned by Avid Life Media, according to The Wall Street Journal.

Avid Life, which also manages matchmaking websites under the CougarLife and Established Men brands, says it has 40 million members around the world.

Two months ago, dating site AdultFriendFinder confirmed it fell victim to a data breach, compromising email addresses, dates of birth and sexual preferences for more than 4 million of its users.