The data includes granular details of pages viewed, buttons clicked and keywords searched. It is matched to the user’s IP address ... and in many cases details

The data includes granular details of pages viewed, buttons clicked and keywords searched. It is matched to the user’s IP address ... and in many cases details of their Facebook account. The ICO (UK data protection regulator) is investigating and it seems the data shared includes "special category" health data which cannot be legally shared with any third parties without explicit consent.