mailpost.exe in MailPost 5.1.1sv, and possibly earlier versions, allows remote attackers to cause a denial of service (server crash), leak sensitive pathname information in the resulting error message, and execute a cross-site scripting (XSS) attack via an HTTP request that contains a / (backslash) and arbitrary webscript before the requested file, which leaks the pathname and does not quote the script in the resulting Visual Basic error message.