GFI MailEssentials AI < 22.4 ListServer.IsDBExist() Absolute Directory Traversal to File Enumeration

GFI MailEssentials AI versions prior to 22.4 contain an arbitrary file existence enumeration vulnerability in the ListServer.IsDBExist() web method exposed at /MailEssentials/pages/MailSecurity/ListServer.aspx/IsDBExist. An authenticated user can supply an unrestricted filesystem path via the JSON key \"path\", which is URL-decoded and passed to File.Exists(), allowing the attacker to determine whether arbitrary files exist on the server.