This vulnerability (CVE-2026-20959) affects Microsoft SharePoint Enterprise Server 2016 (version 16.0.0). It is classified as CWE-79, indicating improper neutralization of input during web page generation, which can lead to cross-site scripting (XSS). An authorized attacker could exploit this flaw to perform spoofing attacks over a network. The CVSS 3.1 base score is 4.6, reflecting a medium severity with network attack vector, low attack complexity, and requiring privileges and user interaction. Microsoft has released an official fix to address this issue.

Successful exploitation could allow an authorized attacker to conduct spoofing attacks by injecting malicious scripts into web pages generated by SharePoint. This may lead to limited confidentiality and integrity impacts but no availability impact. The vulnerability requires the attacker to have some privileges and user interaction to exploit.

An official fix is available from Microsoft. Users of Microsoft SharePoint Enterprise Server 2016 (version 16.0.0) should apply the vendor-provided patch as detailed in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20959 to remediate this vulnerability.