Included in the exposed personal information are customers' email addresses, usernames, passwords, birthdays and zip codes, in addition to their sexual preferences.
No credit card data has yet been uncovered as part of the hack.
This isn't even the first time Adult Friend Finder has been hacked.
It's not clear who was behind the attack, though Leaked Source says it occurred in October 2016.
Adult Friend Finder asks customers to detail their interests and, based on those criteria, matches people for sexual encounters.
The site, which boasts 64 million members, claims to have "helped millions of people find traditional partners, swinger groups, threesomes, and a variety of other alternative partners." The information Adult Friend Finder collects is extremely personal in nature.
That data is incredibly revealing and potentially damaging.
Andrew Auernheimer, a controversial computer hacker who looked through the files, used Twitter to publicly identify Adult Friend Finder customers, including a Washington police academy commander, an FAA employee, a California state tax worker and a naval intelligence officer who supposedly tried to cheat on his wife.