A new study from the Wall Street Journal this week confirmed that third-party applications are providing users’ private information to Facebook, including sensitive health information like menstrual cycles. The user data could be used to better target advertising according to the Journal.

A study that was conducted by the Wall Street Journal and published on Friday confirmed suspicions that Facebook is collecting private information from third-party applications. This private information that was sent to Facebook ranged from personal health matters like menstrual cycles to “Favorited homes” on real estate applications like Realtor.com.

One part of the study revealed that a third-party application for managing menstrual cycles sent private health data to Facebook. The app, Flo, says in their privacy policy that they will not share “information regarding your marked cycles, pregnancy, symptoms, notes and other information that is entered by you and that you do not elect to share.”

After learning that her private information had been shared, the woman who used the app as part of the WSJ study said that she may delete the app. “I think it’s incredibly dishonest of them that they’re just lying to their users especially when it comes to something so sensitive,” the woman said.

The study revealed that more than 70 popular apps on the Apple iOS store were sending private user data to Facebook. Fortunately, apps that track your finances were not found to be sharing private information with third-parties like Facebook. However, a significant portion of the most popular health apps on the app store were immediately sending private data to Facebook immediately after it was entered by the user.

The Journal tested more than 70 apps that are among the most popular in Apple’s iOS store in categories that handle sensitive user information. The Journal used software to monitor the internet communications triggered by using an app, including the information being sent to Facebook and other third parties. The tests found at least 11 apps sent Facebook potentially sensitive information about how users behaved or actual data they entered. Among the top 10 finance apps in Apple’s U.S. app store as of Thursday, none appeared to send sensitive information to Facebook, and only two sent any information at all. But at least six of the top 15 health and fitness apps in that store sent potentially sensitive information immediately after it was collected.

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