CVE-2020-1499 in SharePoint Foundation
Summary
by MITRE
A spoofing 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. These 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 • 02/23/2026
This vulnerability represents a critical cross-site scripting flaw in Microsoft SharePoint Server that stems from inadequate input validation and sanitization mechanisms. The vulnerability manifests when the server fails to properly sanitize specially crafted web requests, creating an avenue for authenticated attackers to exploit the weakness. According to CWE-79, this falls under the category of Cross-Site Scripting, specifically representing a failure to sanitize input that allows malicious scripts to be executed in the context of the current user. The vulnerability is particularly dangerous because it requires only authentication to exploit, meaning that any user with valid credentials can potentially leverage this flaw to compromise the system.
The operational impact of this vulnerability extends far beyond simple script execution, as it enables attackers to perform a comprehensive range of malicious activities within the SharePoint environment. When successfully exploited, the vulnerability allows attackers to execute scripts in the security context of the authenticated user, which creates a pathway for unauthorized data access, privilege escalation, and content manipulation. Attackers can read content that they should not have access to, effectively bypassing authorization controls and potentially accessing sensitive information. The ability to use victim identities to perform actions on the SharePoint site represents a significant escalation risk, allowing malicious actors to modify permissions, delete content, and alter system configurations. This aligns with ATT&CK technique T1078.004 which covers Valid Accounts with the specific focus on legitimate credentials being used to gain access to systems. The injection of malicious content into user browsers creates a persistent threat vector that can affect multiple users within the organization.
The exploitation process involves an authenticated attacker sending specially crafted requests to the SharePoint server, which then processes these requests without proper sanitization, allowing the malicious payload to execute. This vulnerability is particularly concerning in enterprise environments where SharePoint servers often serve as central collaboration platforms containing sensitive business information, documents, and user data. The security update addresses this issue by implementing proper request sanitization mechanisms that validate and clean input before processing, thereby preventing the execution of malicious scripts. Organizations should consider implementing additional security controls such as web application firewalls, regular security assessments, and monitoring for suspicious request patterns to mitigate the risk associated with this vulnerability. The remediation process requires careful planning to ensure that the update does not disrupt legitimate business operations while effectively addressing the security gap. Given the potential for privilege escalation and unauthorized data access, this vulnerability should be prioritized for immediate remediation, especially in environments where SharePoint servers handle sensitive information and where user authentication is a standard requirement for system access.