source: https://www.securityfocus.com/bid/21513/info
  
Messageriescripthp is prone to multiple input-validation vulnerabilities, including SQL-injection and cross-site scripting issues, because it fails to sufficiently sanitize user-supplied data.
  
Exploiting these issues could allow an attacker to steal cookie-based authentication credentials, compromise the application, access or modify data, or exploit latent vulnerabilities in the underlying database implementation.
  
Messageriescripthp V2.0 is vulnerable to this issue.

http://www.example.com/[script_messagerie_path]/existeemail.php?email=[XSS]