Data breaches that reveal email address, usernames, passwords, and other account information are common and pretty serious in their own right – but when a hack reveals even more sensitive personal information it’s downright scary.

According to a report from Channel4, a data breach has exposed nearly four million users of Adult FreindFinder, a dating website. you’ve probably seen its ads all over the internet.

And alongside the usual account information, hackers reportedly leaked info like users’ sexual orientation and “which ones might be seeking extramarital affairs.”

Yikes.

“The stolen data reveals the sexual preferences of users, whether they’re gay or straight, and even indicates which ones might be seeking extramarital affairs. In addition, the hackers have revealed email addresses, usernames, dates of birth, postal codes and unique internet addresses of users’ computers,” reports Channel4.

“Online crime experts believe the after the initial spam email campaign, hackers will now begin trawling through the data for potential blackmail targets. The spreadsheets contain addresses linked to dozens of government and armed services personnel, including members of the British Army.”

Adult FriendFinder’s parent company confirmed the data breach in a statement to the BBC, but didn’t provide a lot of details:

FriendFinder Networks Inc. has only just been made aware of this potential issue and understands and fully appreciates the seriousness of the issue,” the firm said in an emailed statement.

We have already begun working closely with law enforcement and have launched a comprehensive investigation with the help of leading third-party forensics expert, Mandiant.

Until the investigation is completed, it will be difficult to determine with certainty the full scope of the incident, but we will continue to work vigilantly to address this potential issue and will provide updates as we learn more from our investigation.

We cannot speculate further about this issue, but rest assured, we pledge to take the appropriate steps needed to protect our customers if they are affected.

There are reports that the hacker attempted to blackmail the site before publishing the data on the dark web. Apparently, Adult FriendFinder wasn’t too keen on that.