After threatening to release salacious details on as many as 37 million customers of the website, which uses the slogan "Life is short. Have an affair," hackers claimed to publish a huge cache of email addresses and credit card data stolen in July.
               
Avid Life Media, which owns Ashley Madison and Established Men, widely described as a "sugar daddy site," did not verify the data was real, but said it was aware of the claim.
               
The hackers used the dark web which is only accessible using a specialized browser.
               
Still within hours, thousands of email addresses from North America and Europe including many linked to corporations and universities sprouted up on other sites as people decrypted the database. It is possible to create an Ashley Madison account using someone else's name and email.
               
The hackers have appointed themselves as "the moral judge, juror, and executioner, seeing fit to impose a personal notion of virtue on all of society," the company said in a statement.
               
"These are illegitimate acts that have real consequences for innocent citizens who are simply going about their daily lives," it said.
               
The Federal Bureau of Investigation (FBI) is investigating the theft alongside the Royal Canadian Mounted Police and local police, it said.
               
The hackers, who call themselves The Impact Team, leaked snippets of the compromised data in July and threatened to publish names and nude photos and sexual fantasies of customers unless Ashley Madison and another site owned by Avid Life were taken down.
               
"Avid Life Media has failed to take down Ashley Madison and Established Men," tech website Wired quoted The Impact Team as saying in a statement accompanying the online dump.
               
"We have explained the fraud, deceit, and stupidity of ALM (Avid Life Media) and their members. Now everyone gets to see their data," the hackers said, according to Wired.