Securing/Hardening your WHMCS installation
There are a number of steps you should take after installing WHMCS to ensure that it is secure. The WHMCS documentation and guides for these procedures are well written and we've linked them here.
- Securing the writeable directories
- Securing the configuration.php file
- Moving the CRON directory
- Restrict the MySQL database users permissions for day-to-day use
These points are covered in the WHMCS Further Security Steps Guide