CVE-2026-69402 in SharePoint
Summary
by MITRE • 09/08/2026
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.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/08/2026
The vulnerability described constitutes a classic instance of Cross-Site Scripting, technically classified under CWE-79: Improper Neutralization of Input During Web Page Generation. This flaw resides within the web application layer of Microsoft Office SharePoint, specifically affecting how user-supplied input is processed and rendered back to clients without adequate sanitization or encoding. In this context, an attacker who possesses valid authentication credentials can inject malicious scripts into pages viewed by other users. The core technical failure lies in the server-side logic that fails to distinguish between executable code and safe data when generating dynamic web content. By exploiting this lack of input validation, the injected script executes within the security context of the victim’s browser session, effectively bypassing same-origin policies designed to isolate different websites from each other.
The operational impact of this vulnerability extends beyond simple defacement or cookie theft, as indicated by the potential for spoofing over a network. When malicious JavaScript is executed in the context of SharePoint, it gains access to sensitive cookies, local storage data, and session tokens associated with the authenticated user’s account. This capability allows an attacker to hijack active sessions, impersonate legitimate users, or perform actions on behalf of those users without their knowledge. The spoofing aspect suggests that the injected content can manipulate the visual presentation of the SharePoint interface, potentially tricking users into entering credentials into a fake login form hosted by the attacker or redirecting them to malicious external domains while maintaining the appearance of legitimacy through URL manipulation and DOM-based tricks.
From an offensive security perspective, this vulnerability aligns with MITRE ATT&CK technique T1059: Command and Control via Web Protocols if used for initial access or lateral movement, but more accurately maps to T1078: Valid Accounts when leveraging the authorized attacker status, and T1136.002: Create Account: Cloud Account if new sessions are created. The exploitation chain typically involves crafting a malicious payload that exploits specific rendering engines within SharePoint, such as those handling rich text fields or custom web parts. Once executed, the script can exfiltrate sensitive corporate data stored in document libraries, modify configuration settings, or propagate further attacks to other users who view the compromised page, creating a persistent threat vector within the enterprise environment.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The most effective technical fix is to implement strict output encoding for all user-supplied data before it is rendered in HTML contexts. This includes using context-aware encoding techniques that convert special characters into their corresponding HTML entities, thereby preventing the browser from interpreting them as executable code. Additionally, deploying Content Security Policy headers can significantly reduce the impact of successful XSS attacks by restricting the sources from which scripts are allowed to load and execute. For Microsoft Office SharePoint specifically, applying the latest cumulative updates and security patches provided by Microsoft is critical, as these often include fixes for known input validation flaws in specific modules or features.
Beyond technical controls, organizational defenses should focus on reducing the attack surface associated with authenticated access. Implementing multi-factor authentication adds a layer of protection even if session tokens are compromised. Regular vulnerability assessments and penetration testing focused on web application security can help identify similar injection points before they are exploited by malicious actors. Furthermore, educating users about phishing techniques that often accompany XSS-based spoofing attacks is essential for maintaining overall security posture. By combining robust input validation practices with comprehensive monitoring and user awareness programs, organizations can effectively mitigate the risks posed by this class of vulnerabilities in their SharePoint environments.