Cross-site scripting (XSS) vulnerability in the web applications in Microsoft Exchange Server 2013 Cumulative Update 8 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors, aka "Exchange HTML Injection Vulnerability."
https://euvd.enisa.europa.eu/vulnerability/EUVD-2015-2452
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-064