A reflected Cross-site Scripting (XSS) vulnerability in web proxy disclaimer response web pages in Fortinet FortiOS 5.6.0, 5.4.0 to 5.4.5, 5.2.0 to 5.2.11 allows an unauthenticated attacker to inject arbitrary web script or HTML in the context of the victim's browser via sending a maliciously crafted URL to the victim.