I found out that the domain
xyz.example.com gives me a 404 error when visited. This domain has the following CNAME >
xyz.example.com.ent.syn-alias.com (same 404 page)
Which is pointing to another CNAME >
xyz.example.com.ent.cmh.syn-alias.com (same 404 page)
I did a quick search and it seems that syn-alias.com is provided by synacor.com
Is this domain vulnerable to subdomain takeover? It doesn't seem that there's a registration page or a check availability page in synacor.com website. How can I test if it's vulnerable to subdomain takeover?