Disable subdomain creation to avoid subdomain Hijack
Hackers can easily make a subdomain from a domain name which they don't own with the option "I will use my existing domain and update my nameservers". when ordering a hosting package.
I request WHMCS to add some feature that could block/ban subdomain creation when "I will use my existing domain and update my nameservers" option is selected upon hosting orders.
Personally, I am afraid to use the auto-activation system of WHMCS. If I enable auto cPanel creation after payment is received, hackers can make a subdomain buy purchasing a web hosting package from a domain name which they don't own.
Therefore, the subdomain could be abused in many ways.
I am not sure if WHMCS would consider this as a bug or not, but this is a serious security issue for my customers.