A reflected Cross-Site Scripting (XSS) vulnerability in Fortinet FortiMail 5.1 and earlier, 5.2.0 through 5.2.9, and 5.3.0 through 5.3.9 customized pre-authentication webmail login page allows attacker to inject arbitrary web script or HTML via crafted HTTP requests.

An unauthenticated XSS vulnerability with FortiMail 5.0.0 - 5.2.9 and 5.3.0 - 5.3.8 could allow an attacker to execute arbitrary scripts in the security context of the browser of a victim logged in FortiMail, assuming the victim is social engineered into clicking an URL crafted by the attacker.