The remote host is vulnerable to a Cross-Site Scripting (XSS) attack.
The remote host is running wwsympa.fcgi, a web interface for the Sympa mailing list manager. It is reported that this version of Sympa may permit an attacker to inject malicious HTML in "List Info" page through the description field of the list creation form. This field is not sanitized properly by the CGI.
Upgrade to version 4.1.3 or higher.