OH: Internal documents Facebook has fought to keep private obtained by UK Parliament.

Six4Three, which has been engaged in a yearslong legal battle with Facebook, were the makers of “Pikini,” a controversial app that allowed users to find pictures of their friends wearing bikinis.

The app did not breach Facebook’s terms and conditions when it was released in 2013. But in 2015 Facebook changed its policies about how it shared information about its users with third-party app developers such as those behind Pikini.

Prior to the change, Pikini and other app developers were able to access information not only about their users, but also about their users’ Facebook friends, including users’ friends’ photos.

When Facebook restricted access to friend data, it destroyed Pikini’s businesses, Six4Three alleges.

While a crude app that searched out bikini photos, and which shut down years ago, might not be noteworthy on its own, the fact that Six4Three has access to internal Facebook documents — currently under court seal — is.

Facebook ought to know better than to trust sensitive information to Facebook.