A Cross-Site Request Forgery (CSRF) vulnerability exists in TeamMate+ 21.0.0.0 that allows a remote attacker to modify application data (upload malicious/forged files on a TeamMate server, or replace existing uploaded files with malicious/forged files). The specific flaw exists within the handling of Upload/DomainObjectDocumentUpload.ashx requests because of failure to validate a CSRF token before handling a POST request.