You should tweak these Facebook privacy settings to prevent your data from unknowingly being shared by friends to third-party harvesters.
https://www.makeuseof.com/tag/facebook-limit-data-shared-third-parties/
* harvested 50 million Facebook profiles * privacy settings * The Complete Facebook Privacy Guide * The Complete Facebook Privacy Guide * App Settings page * prevent Facebook from selling your browsing data * How to Stop Facebook From Selling Your Browsing Data * How to Stop Facebook From Selling Your Browsing Data