CVE-2026-88208 in SharePoint
Summary
by MITRE • 10/14/2026
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 • 10/14/2026
The vulnerability described constitutes a classic instance of Cross-Site Scripting, formally 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 execution flow, an attacker who possesses valid authentication credentials for the SharePoint environment can inject malicious script payloads into fields that are subsequently rendered by the browser without proper encoding. Because the application treats this untrusted data as executable code rather than inert text, the injected scripts run with the same privileges and context as legitimate page content within the victim's browser session.
From a technical perspective, the core deficiency lies in the absence of robust output encoding or input validation mechanisms at the point where user data is embedded into the Document Object Model. When an authorized user interacts with a vulnerable component, such as a discussion board post, wiki entry, or custom web part configuration, their malicious payload becomes part of the page structure. Modern browsers execute these scripts immediately upon rendering, allowing the attacker to manipulate the DOM, steal session cookies, capture keystrokes, or perform actions on behalf of the user. The presence of authentication requirements means this is not a remote code execution vulnerability accessible to anonymous users, but rather an authenticated attack vector that exploits trust relationships within the intranet environment.
The operational impact of this vulnerability extends beyond simple script injection. As noted in the description, it allows for spoofing over a network, which aligns with MITRE ATT&CK technique T1078: Valid Accounts and potentially T1566: Phishing if used to deceive users into clicking malicious links generated by the exploit. An attacker can craft deceptive pages that mimic legitimate SharePoint interfaces or internal applications, leading to credential harvesting through phishing simulations or actual social engineering attacks. Furthermore, because the script executes in the context of the authenticated user, it enables session hijacking and privilege escalation within the application logic itself. The attacker can access sensitive documents, modify site configurations, or exfiltrate data that would otherwise be protected by SharePoint’s permission model, effectively bypassing security controls through client-side manipulation rather than server-side exploitation.
Mitigation strategies for this vulnerability require a multi-layered approach focusing on both immediate remediation and long-term architectural improvements. The most effective technical countermeasure is the implementation of strict output encoding using context-aware methods such as HTML entity encoding or JavaScript string escaping, ensuring that special characters are converted to their safe equivalents before rendering. Additionally, enabling Content Security Policy headers can significantly restrict the execution environment by preventing inline script execution and limiting sources from which scripts can be loaded. From a defensive posture perspective, organizations should enforce least-privilege access controls for SharePoint users, regularly patching the server software to ensure that Microsoft’s security updates addressing this specific flaw are applied promptly. User awareness training is also critical to mitigate the social engineering aspects associated with spoofing attacks derived from such vulnerabilities.