I'm the owner of a hypothetical domain name, XYZ.com. I have an LXC container setup that exhibits an undesired behavior:
$ nslookup non-existent-domain-12345.com Name: non-existent-domain-12345.com.XYZ.com Address: W.X.Y.Z
Somewhere, I have a misconfiguration. The system knows that my domain is XYZ.com, and decides to map any non-existing domain to be a subdomain of my primary domain.