A wildcard certificate is a domain validated certificate that secures all subdomains of the specified domain, but only on one level.
A wildcard certificate of *.example.org will matches www.example.org, but will not match example.org and www.sub.example.org
To resolve this problem, generally the domain validated certificate uses the Subject Alternative Name (SubjectAltName) field to list the domain.
For instance:
DNS Name=*.www.example.org
DNS Name=www.example.org
DNS Name=example.org
DNS Name=*.example.org