That makes the attack nearly as big as the recently reported Yahoo hack and potentially as explosive in its implications as the 2015 breach of Ashley Madison, another adult-focused social network facilitating extramarital affairs.

Approximately 339 million user accounts were hacked from Adult Friend Finder itself. A previous hack of AdultFriendFinder data exposed users’ sexual preferences and marital status along with birth dates and email addresses. According to ZDNet, the current breach includes less intimate data, instead including primarily usernames, email addresses, and passwords.

The breach also included data from 15 million deleted accounts that were apparently not scrubbed from the site’s databases, data from other FriendFinder Networks properties including cams.com, and data from Penthouse.com, which was owned by FriendFinder Networks before being sold to a relaunched Penthouse Global Media in February.

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The culprit in the breach has not been identified. ZDNet independently verified the data, but FriendFinder Networks has not yet publicly acknowledged the extent of the breach.

Beyond the security implications, the attack could prove personally damaging to users, who could be identified, for instance, by their email addresses. Unlike a traditional dating site, AdultFriendFinder bills itself as a place for “sex dating,” where users can find “swinger groups, threesomes, and a variety of other alternative partners.” Membership to such a service could be a liability for anyone with a public image at odds with alternative sexualities.

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A similar scenario played out during the fallout from the Ashley Madison hack. The two sites are not entirely comparable as Ashley Madison explicitly offered a digital meeting place for married people to cheat on their spouses. But that hack tarnished the images and harmed the careers of government workers, politicians, prosecutors, and media figures as well as private citizens.