CVE-2020-1580 in SharePoint Foundation
Summary
by MITRE
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. 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. The security update addresses the vulnerability by helping to ensure that SharePoint Server properly sanitizes web requests.
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Analysis
by VulDB Data Team • 02/24/2026
The vulnerability identified as CVE-2020-1580 represents a critical cross-site scripting weakness in Microsoft SharePoint Server that stems from inadequate input sanitization mechanisms. This flaw resides in the server's handling of web requests, specifically when processing specially crafted inputs that bypass normal security validation procedures. The vulnerability operates at the application layer and affects SharePoint Server implementations that fail to properly validate and sanitize user-supplied data before processing or rendering it within web responses. The security implications are particularly severe because the flaw affects authenticated users, meaning that an attacker must first establish valid credentials to exploit the vulnerability, but once successful, the attack can be executed within the context of the compromised user's session. The vulnerability is categorized under CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') which is a fundamental web application security weakness that has been consistently identified as one of the most prevalent and dangerous vulnerabilities in web applications.
The operational impact of this vulnerability extends far beyond simple script injection, as successful exploitation allows attackers to perform a comprehensive range of malicious activities within the SharePoint environment. When an authenticated attacker successfully leverages this vulnerability, they can execute scripts in the security context of the current user, effectively enabling them to impersonate legitimate users within the system. This capability allows for unauthorized data access, where attackers can read content that they would normally not have permission to view, effectively bypassing access control mechanisms. The attacker can also use the victim's identity to perform actions on the SharePoint site, including modifying permissions, deleting content, and creating new user accounts with elevated privileges. Additionally, the vulnerability enables the injection of malicious content directly into users' browsers, which can result in further exploitation such as credential theft, session hijacking, or redirection to malicious sites. This type of attack aligns with ATT&CK technique T1566.001 - Phishing: Spearphishing Attachment, where the malicious script serves as a payload that can be delivered through compromised SharePoint pages. The attack chain typically begins with an authenticated user visiting a maliciously crafted SharePoint page, which then executes the injected script in the user's browser context, allowing the attacker to maintain persistent access to the compromised system.
Microsoft addressed this vulnerability through a security update that enhances the SharePoint Server's input sanitization capabilities, ensuring that web requests containing potentially malicious content are properly validated and sanitized before being processed or rendered. The fix involves strengthening the server's validation logic to identify and neutralize dangerous input patterns that could lead to XSS attacks. Organizations should implement this update immediately as part of their patch management strategy, particularly given that the vulnerability requires authentication to exploit, which means that the attack surface is limited to users with valid credentials. However, the severity remains high because compromised accounts can provide attackers with significant privileges within the SharePoint environment, potentially leading to complete system compromise. The mitigation strategy should also include implementing additional security controls such as web application firewalls, input validation rules, and regular security assessments to identify potential weaknesses in the SharePoint implementation. Security teams should also consider implementing monitoring solutions that can detect unusual activity patterns that might indicate exploitation attempts, as the vulnerability's impact is directly tied to the execution of malicious scripts within user sessions, which may not be immediately apparent to system administrators.