CVE-2020-1198 in SharePoint Server
Summary
by MITRE
<p>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. An authenticated attacker could exploit the vulnerability by sending a specially crafted request to an affected SharePoint server.</p> <p>The attacker who successfully exploited the vulnerability could then perform cross-site scripting attacks on affected systems and run script in the security context of the current user. The attacks could allow the attacker to read content that the attacker is not authorized to read, use the victim's identity to take actions on the SharePoint site on behalf of the user, such as change permissions and delete content, and inject malicious content in the browser of the user.</p> <p>The security update addresses the vulnerability by helping to ensure that SharePoint Server properly sanitizes web requests.</p>
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Analysis
by VulDB Data Team • 02/24/2026
The vulnerability identified as CVE-2020-1198 represents a critical cross-site scripting flaw within Microsoft SharePoint Server that stems from inadequate input validation mechanisms. This weakness allows authenticated attackers to manipulate web requests in ways that bypass the server's sanitization protocols, creating a persistent security risk for organizations relying on SharePoint infrastructure. The vulnerability specifically targets the server's handling of crafted web requests, where the sanitization process fails to properly neutralize malicious script content, thereby enabling attackers to inject harmful code into the server's response handling mechanisms.
The technical exploitation of this vulnerability occurs through authenticated sessions, meaning that an attacker must first establish valid credentials within the SharePoint environment before attempting to leverage the XSS flaw. This authentication requirement slightly limits the attack surface compared to unauthenticated vulnerabilities but does not eliminate the severity of the threat. When successfully exploited, the vulnerability allows attackers to execute arbitrary script code within the security context of legitimate users, effectively granting them the ability to operate with the privileges and permissions of the compromised user account. This fundamental breach of isolation enables attackers to perform a wide range of malicious activities that would otherwise be restricted by normal access controls.
The operational impact of CVE-2020-1198 extends far beyond simple script injection, as it provides attackers with comprehensive access to sensitive SharePoint functionality and data. An attacker who successfully exploits this vulnerability can read content that they would normally not have authorization to access, effectively bypassing content access controls and potentially gaining access to confidential information. The ability to impersonate users enables attackers to perform privileged actions such as modifying permissions, deleting content, and altering site configurations. Furthermore, the injected malicious scripts can persistently target other users within the SharePoint environment, creating a vector for widespread compromise. This vulnerability directly violates the principle of least privilege and can lead to complete compromise of SharePoint sites and the data they contain.
Microsoft's security update for this vulnerability addresses the core sanitization issue by implementing enhanced input validation mechanisms that properly neutralize potentially malicious content within web requests. The fix ensures that SharePoint Server properly processes and sanitizes all incoming requests, eliminating the conditions that previously allowed XSS payloads to be executed. Organizations should prioritize applying this update as part of their vulnerability management processes, particularly given the authenticated nature of the attack vector which suggests that internal threats or compromised accounts could be leveraged to exploit this weakness. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and represents a classic example of insufficient input sanitization that can be exploited through the ATT&CK technique of Web Shell deployment and credential access through session hijacking.
The broader implications of CVE-2020-1198 highlight the critical importance of input validation in enterprise web applications, particularly in collaborative platforms like SharePoint where user-generated content and permissions management create complex security challenges. Organizations should implement additional monitoring and detection measures to identify potential exploitation attempts, including web application firewall rules that can detect suspicious request patterns and behavioral analysis systems that can identify anomalous user activities. The vulnerability demonstrates how seemingly minor input validation failures can create significant security risks in complex enterprise environments where SharePoint servers often serve as central repositories for sensitive business information and collaborative workspaces.