Silverpeas 6.4.2 contains a stored cross-site scripting (XSS) vulnerability in the event management module. An authenticated user can upload a malicious SVG file as an event attachment, which, when viewed by an administrator, executes embedded JavaScript in the admin's session. This allows attackers to escalate privileges by creating a new administrator account. The vulnerability arises from insufficient sanitization of SVG files and weak CSRF protections.