1 - Log in as an agent
2 - Write a new message to user goadmin with random subject and text
3 - Attach your webshell to the message
4 - Access your shell at
https://www.foo.com/uploads/year/month/shellname.php ( Example:
https://XXX.XXX.XXX.XXX/uploads/2020/07/shell.php )
5 - Priv esc and enjoy ... :-)