KLA10657
Multiple vulnerabilities in Microsoft communication services

Improper content sanitization at jQuery engine and other vectors were found in Lync Server and Skype for Business Server. By exploiting these vulnerabilities malicious users can gain privileges or obtain sensitive information. These vulnerabilities can be exploited remotely via a specially designed web content. Clients connected to affected servers are also affected.

Lync Server 2013
Skype for Business Server 2015

Install necessary updates from the KB section, that are listed in your Windows Update (Windows Update usually can be accessed from the Control Panel)