Microsoft Skype for Business Server Federation is a functionality that enables you to communicate with other people outside your organization by using a Skype for Business client. Therefore, you may be concerned about the manner in which communication is conducted with external users (especially anonymous and federated users) and also about privacy and Data Leakage Protection (DLP).
After you apply this update, your ability to do a file transfer can be disabled by the Skype for Business Server administrators, regardless of whether you're in a peer-to-peer session or a conference call. You will see a notification that explains why attempts to transfer a file are failing in Skype for Business 2016.
How to get this update
To get this update, install the October 2, 2018, update (KB4092445) for Skype for Business 2016.