This vulnerability (CVE-2026-55020) 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 leads to cross-site scripting. The flaw allows an attacker with authorized access to conduct spoofing attacks over a network. The CVSS 3.1 base score is 4.6 (medium severity), with attack vector network, low attack complexity, requiring privileges and user interaction, and impacts confidentiality and integrity. Microsoft has released an official fix for this vulnerability as documented in their security update guide.

An authorized attacker can exploit this vulnerability to perform cross-site scripting attacks, potentially leading to spoofing and limited compromise of confidentiality and integrity within the affected SharePoint environment. There is no impact on availability. No known exploits are reported in the wild at this time.

An official fix is available from Microsoft. It is recommended to apply the security update provided in the Microsoft advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55020 to remediate this vulnerability.