[calculito]

ok, it's easy for you to understand. For some other people, me for example, not that easy. The question is also, how is is possible. So, I don't expect a detailed explanation or a step-by-step howTo but do you have any hints?

[ahazred8ta]

Other commenters have suggested that the xyz site is not using telepathy to instantly update itself whenever you make a change, but rather they have no local copy of your site at all, and every time you load an xyz page, it fetches the contents directly from your site. Some are assuming that the foo.xyz DNS is pointing at your own server, but you say you've checked for that.

[cranberryturkey]

its called 'web scraping' look it up. You can send a cease and desist or block their ips.

[jrvieira]

Server side code is not publicly accessible, that's not what webscraping means, and nothing is being copied in this case, it's being proxied.