A cross-site-scripting (XSS) vulnerability exists when Microsoft SharePoint Server does not properly sanitize a specially crafted web request to an affected SharePoint server, aka 'Microsoft Office SharePoint XSS Vulnerability'.
https://www.tenable.com/blog/microsofts-september-2019-patch-tuesday-tenable-roundup
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1262
http://packetstormsecurity.com/files/154591/Microsoft-SharePoint-2013-SP1-Cross-Site-Scripting.html