Vulnerabilities in SharePoint could allow elevation of privilege
Description
Microsoft SharePoint contains a cross-site scripting (XSS) vulnerability that enables attackers to inject and execute malicious JavaScript in the context of authenticated users. When a user clicks a specially crafted link, the attacker's script executes with the victim's privileges, effectively allowing an unauthenticated attacker to perform actions on behalf of legitimate SharePoint users. This constitutes an elevation of privilege vulnerability because it grants anonymous attackers the ability to execute SharePoint operations with authenticated user permissions.
Remediation
Apply the security updates provided in Microsoft Security Bulletin MS12-050 immediately. Follow these steps to remediate the vulnerability:
1. Install Security Updates:
• Download and install the appropriate security update for your SharePoint version from the Microsoft Security Bulletin MS12-050.
• Test the update in a non-production environment before deploying to production systems.
• Schedule maintenance windows to apply updates to all affected SharePoint servers.
2. Verify Patch Installation:
• Confirm successful installation through Windows Update or the SharePoint Central Administration console.
• Review system logs for any installation errors or issues.
3. Implement Defense-in-Depth Measures:
• Enable Content Security Policy (CSP) headers to restrict script execution sources.
• Implement input validation and output encoding for all user-supplied data in custom SharePoint solutions.
• Use SharePoint's built-in XSS protection features and ensure they are not disabled.
• Educate users about the risks of clicking untrusted links, especially those leading to SharePoint sites.
4. Monitor and Audit:
• Review SharePoint access logs for suspicious activity or anomalous user behavior.
• Implement monitoring for unusual JavaScript execution patterns or unauthorized privilege escalation attempts.