The ASG/ProxySG FTP proxy WebFTP mode allows intercepting FTP connections where a user accesses an FTP server via a ftp:// URL in a web browser. A stored cross-site scripting (XSS) vulnerability in the WebFTP mode allows a remote attacker to inject malicious JavaScript code in ASG/ProxySG's web listing of a remote FTP server. Exploiting the vulnerability requires the attacker to be able to upload crafted files to the remote FTP server. Affected versions: ASG 6.6 and 6.7 prior to 6.7.4.2; ProxySG 6.5 prior to 6.5.10.15, 6.6, and 6.7 prior to 6.7.4.2.