Cross-site scripting (XSS) vulnerability in Microsoft Excel Services on SharePoint Server 2010 SP2 and 2013 SP1, Office Web Apps 2010 SP2, Excel Web App 2010 SP2, Office Web Apps Server 2013 SP1, and SharePoint Foundation 2013 SP1 allows remote authenticated users to inject arbitrary web script or HTML via a crafted URL, aka "Microsoft Office Web Apps XSS Spoofing Vulnerability."
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2015/ms15-110