Cross-site scripting (XSS) vulnerability in Outlook Web Access (OWA) in Microsoft Exchange Server 2013 Cumulative Update 8 and 9 and SP1 allows remote attackers to inject arbitrary web script or HTML via a crafted e-mail message, aka "Exchange Spoofing Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-103