CVE-2026-69690 in SharePoint Server
Summary
by MITRE • 09/09/2026
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office SharePoint allows an authorized attacker to perform spoofing over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described constitutes a classic instance of Cross-Site Scripting, specifically categorized under CWE-79: Improper Neutralization of Input During Web Page Generation. This flaw resides within the web application layer of Microsoft Office SharePoint Server, where the system fails to adequately sanitize or validate user-supplied input before incorporating it into dynamically generated HTML content. In a typical exploitation scenario, an attacker who possesses valid authentication credentials injects malicious script code, often in the form of JavaScript, into fields that are rendered directly by the server without proper encoding or escaping mechanisms. Because SharePoint is a collaborative platform frequently used for internal communications and document management, this vulnerability poses a significant risk to organizational security infrastructure.
The operational impact of this flaw extends beyond simple defacement or session hijacking, as noted in the initial description regarding spoofing capabilities. By executing arbitrary scripts within the context of the trusted SharePoint domain, an attacker can bypass same-origin policy restrictions inherent to web browsers. This allows the malicious code to access sensitive cookies, local storage data, and other protected resources associated with the user's active session. The ability to perform network-level spoofing implies that the injected script can forge requests on behalf of the authenticated victim, potentially manipulating form submissions or API calls without the user's knowledge. This undermines the integrity of interactions between the client browser and the SharePoint server, allowing attackers to alter data, steal sensitive documents, or escalate privileges within the application logic if combined with other vulnerabilities.
From a threat intelligence perspective, this vulnerability aligns with several techniques in the MITRE ATT&CK framework. It is primarily associated with T1059: Command and Scripting Interpreter, specifically through client-side scripting such as JavaScript. Furthermore, the potential for session hijacking and credential theft maps to T1539: Steal Web Session Cookie, while the spoofing aspect relates to T1621: Multi-Factor Authentication Request Interception if multi-factor authentication is in place but bypassed via script injection. The attack vector requires prior authorization, classifying this as an insider threat or a post-exploitation scenario where initial access has already been gained through compromised credentials or social engineering.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. Microsoft typically releases security updates to patch such vulnerabilities; therefore, applying the latest cumulative update for the specific version of SharePoint Server is the primary corrective action. Administrators should also implement strict Content Security Policy headers to restrict the execution of unauthorized scripts and define allowed sources for content loading. Input validation must be enforced at multiple layers, ensuring that all user inputs are encoded according to their context within HTML, JavaScript, or URL structures before being processed by the server-side rendering engine. Additionally, enabling HTTP-only flags on session cookies can prevent client-side scripts from accessing them, thereby mitigating the risk of session hijacking even if script injection succeeds. Regular security audits and penetration testing focused on web application vulnerabilities are essential to identify similar flaws in custom SharePoint solutions or third-party add-ons that may not be covered by standard patches.