CVE-2026-97783 in SharePoint Server
Summary
by MITRE • 10/15/2026
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office SharePoint allows an unauthorized attacker to perform spoofing over a network.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability described constitutes a classic Cross-Site Scripting (XSS) flaw within the Microsoft Office SharePoint environment, specifically categorized under CWE-79: Improper Neutralization of Input During Web Page Generation. This security defect arises from an application's failure to properly validate or sanitize user-supplied input before including it in dynamically generated web pages. In this context, the server-side processing logic accepts untrusted data and embeds it directly into HTML output without adequate encoding or filtering mechanisms. Consequently, when a victim user views the affected page through their web browser, the malicious script embedded within that content is executed by the client-side runtime environment rather than being treated as inert text. This fundamental breakdown in input validation allows an attacker to inject arbitrary JavaScript code into the context of the trusted SharePoint domain, effectively bypassing same-origin policy restrictions and leveraging the trust relationship between the user's browser and the application server.
From a technical perspective, this vulnerability enables an unauthorized actor to perform spoofing operations over a network by manipulating the client-side state and behavior. By executing scripts in the security context of the SharePoint site, the attacker can access sensitive cookies, session tokens, or other authentication credentials stored locally within the browser. This capability facilitates account hijacking, allowing the adversary to impersonate legitimate users without needing their passwords. Furthermore, the injected script can perform actions on behalf of the victim, such as modifying page content, redirecting users to phishing sites that mimic SharePoint interfaces, or harvesting sensitive information entered into forms. The attack vector typically involves tricking a user into clicking a malicious link containing the payload in query parameters or form fields, although stored XSS variants could persist the script within database records for broader impact against multiple victims visiting specific pages.
The operational impact of this vulnerability is significant due to its potential to compromise confidentiality and integrity within an enterprise collaboration environment. SharePoint often serves as a central repository for critical business documents and communication channels; therefore, compromising user sessions can lead to unauthorized access to proprietary data or the insertion of malicious content into shared workspaces. Attackers may use this foothold to launch further attacks against internal network resources if session tokens provide elevated privileges or allow lateral movement within the organization's infrastructure. Additionally, the ability to spoof identities undermines trust in digital communications and document integrity, potentially leading to reputational damage and regulatory non-compliance depending on the sensitivity of the data involved. The ease of exploitation means that even low-skilled attackers can leverage existing exploit kits or custom scripts to target vulnerable instances, making this a persistent threat vector for organizations relying heavily on web-based collaboration tools.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. Immediately, Microsoft should apply the latest security patches and updates released for the affected versions of Office SharePoint Server, which typically include code fixes that enforce stricter input validation rules. Administrators should also ensure that Content Security Policy (CSP) headers are implemented to restrict the sources from which scripts can be loaded, thereby mitigating the impact of any successfully injected payloads by preventing execution of unauthorized JavaScript. On a development and configuration level, developers must adopt secure coding practices such as output encoding specific to the context where data is rendered, utilizing parameterized queries for database interactions, and implementing robust input validation frameworks that reject or sanitize potentially dangerous characters like angle brackets and quotes. Regular security assessments, including static code analysis and dynamic penetration testing focused on XSS vectors, are essential to identify and rectify similar flaws before they can be exploited in production environments.