This vulnerability is caused when SharePoint Server does not properly sanitize a specially crafted request to an affected SharePoint server.An authenticated attacker could exploit this vulnerability by sending a specially crafted request to an affected SharePoint server, aka 'Microsoft SharePoint Reflective XSS Vulnerability'. This CVE ID is unique from CVE-2020-0795.
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0891