Wildcard SSLs are an inexpensive option, whilst also effective, to allow you to utilize a multitude of sub-domains and cover every single one using a single certificate. This will save you a lot of time and effort, while bolstering your sites overall security without making any compromises or leaving any potential weak points which could be exploited by malicious third parties. The benefits of adopting a wildcard SSL certificate include providing instant coverage of subdomains from the moment they are created, without gaps during which your site is exposed.”]
Source: https://gbhackers.com/main-issues-wildcard-ssl-certificate-can-solve/