CVE-2020-1103

An information disclosure vulnerability exists where certain modes of the search function in Microsoft SharePoint Server are vulnerable to cross-site search attacks (a variant of cross-site request forgery, CSRF).
When users are simultaneously logged in to Microsoft SharePoint Server and visit a malicious web page, the attacker can, through standard browser functionality, induce the browser to invoke search queries as the logged in user.  While the attacker can’t access the search results or documents as such, the attacker can determine whether the query did return results or not, and thus by issuing targeted queries discover facts about documents that are searchable for the logged-in user.
The security update addresses the vulnerability by running the search queries in a way that doesn’t expose them to this browser vulnerability.