An SSL certificate that protects multiple subdomains on a single site. For example, one wildcard certificate can be used to sign resources located on the domains:
- example.com
- test.example.com
- promo.example.com
- www.example.com
Since the certificate covers only one level of subdomains, the site www.test.example.com would not be able to use the same digital signature. RFC 6125 discourages the use of wildcard certificates on security grounds.