Failure to sanitize input in the SSL VPN web portal of FortiOS 5.2.10 through 5.2.15 5.4.0 through 5.4.13 5.6.0 through 5.6.14 6.0.0 through 6.0.12 6.2.0 through 6.2.7 6.4.0 through 6.4.4; and FortiProxy 1.2.0 through 1.2.9 2.0.0 through 2.0.1 may allow a remote unauthenticated attacker to perform a reflected Cross-site Scripting (XSS) attack by sending a request to the error page with malicious GET parameters.