GitHub Pages allows to set up a public page under
<user>.github.io that can optionally be customized with a personal domain. In order to do so:
- GitHub must be set up to recognize that an incoming call referred to by a non-GitHub domain should be handled
- the personal domain must have a pointer to GitHub, via a
CNAMEin the domain's zone
At some point in the documentation, there is a fat warning:
(EDIT: I updated the example below to a more complete zone following Steffen's answer because I do not understand it)
Let's say that I own
example.com and the public IP
18.104.22.168, and I have a wildcard DNS entry:
*.example.com. IN CNAME hello.example.com. hello.example.com. 300 IN A 22.214.171.124 mypageongithub.example.com. IN CNAME myuser.github.io.
In other words, something not otherwise defined in my
example.com zone points to
How can this present a danger of someone using my domain to advertise their GitHub page?
Note: I posted the question in Information Security rather than superuser.com or another similar site as this is more about identity theft (or misrepresentation) than a technical question about DNS