🟠 High | Source: Microsoft Security Response Center
A cross-site scripting (XSS) vulnerability in Microsoft SharePoint allows an authenticated attacker to inject malicious scripts into web pages viewed by other users, enabling spoofing attacks over a network. Because the attacker only needs an existing account to exploit this, the barrier to attack is relatively low. If successfully exploited, this could be used to steal session tokens, redirect users to malicious sites, or impersonate legitimate users.
Security Architect’s Take: Ensure all SharePoint instances — both SharePoint Online and on-premises Server — are patched promptly via Microsoft’s update guidance. In the interim, consider reviewing and tightening Content Security Policy (CSP) headers on SharePoint sites and auditing user permissions to limit the pool of authorised accounts that could be leveraged.
Original advisory: CVE-2026-57105 Microsoft Office SharePoint Spoofing Vulnerability