KLA10591
Code injection in Microsoft Exchange Server

Multiple XSS vulnerabilities were found in Microsoft Exchange Server. By exploiting these vulnerabilities malicious users can inject arbitrary web script or spoof user interface. These vulnerabilities can be exploited remotely via a specially designed URL, msgParam or other unknown vectors.

Microsoft Exchange Server 2013 Service Pack 1
Microsoft Exchange Server 2013 Cumulative Update 7

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