Information is leak in error page and this can support for other vulnerabilities.
Whenever trying to input anything meaningless after the link https://rdiffweb-demo.ikus-soft.com/ the error page will appear.
Example: https://rdiffweb-demo.ikus-soft.com/*
https://rdiffweb-demo.ikus-soft.com/’
https://rdiffweb-demo.ikus-soft.com/admin/