A German court today ruled that WhatsApp violates the data protection law and WhatsApp users can be warned theoretically. When using WhatsApp, the phone numbers of all contacts in the address book are automatically passed on to the messenger. According to the judgment of the District Court of Bad Hersfeld (Germany), WhatsApp thereby violates the right of the users to informational self-determination. The judgment ultimately affects not only private users, but also companies and authorities that use WhatsApp for business purposes. Many enterprises are now wondering how they could be affected by warnings and how they can protect themselves against such warnings.