Toxssin : An XSS Exploitation Command-Line Interface

Toxssin is an open-source penetration testing tool that automates the process of exploiting Cross-Site Scripting (XSS) vulnerabilities. It consists of an https server that works as an interpreter for the traffic generated by the malicious JavaScript payload that powers this tool (toxin.js).

This project started as (and still is) a research-based creative endeavor to explore the exploitability depth that an XSS vulnerability may introduce by using vanilla JavaScript, trusted certificates and cheap tricks.

TABLE OF CONTENTS

1 Capabilities
2 Installation & Usage
3 XSS Exploitation Obstacles
4 How to get a Trusted Certificate
5 Changelog
6 Future
- 6.1 About The Author
  - 6.1.1 Prakash
- 6.2 Related

Capabilities

By default, toxssin’s JavaScript poison automatically spreads across the elements and information of a webpage, abusing the XMLHttpRequest object to intercept:

cookies (if HttpOnly not present),
keystrokes (technically, an active keylogger),
paste events,
input change events,
file selections,
form submissions,
server responses (to form submissions or clicking hyperlinks that target different pages and not internal parts of the same page),
table data (static as well as updates on tables after a page has finished loading),

Most importantly, toxssin:

attempts to create XSS persistence while the user browses the website by intercepting http requests & responses and re-writing the document, creating the illusion of navigating when actually the document’s location never changes,
supports session management (you can use it to exploit multiple targets at the same time e.g., by running an XSS-based phishing campaign or exploiting stored XSS),
supports custom JS script execution against sessions (after a browser gets hooked, you can run custom JS scripts against it),
automatically logs every session.

Installation & Usage

git clone https://github.com/t3l3machus/toxssin
cd ./toxssin
pip3 install -r requirements.txt

To start toxssin.py, you will need to supply ssl certificate and private key files.

If you don’t own a domain with a trusted certificate, you can issue and use self-signed certificates with the following command (although this won’t take you far):

openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 365

It is strongly recommended to run toxssin with a trusted certificate (see How to get a Valid Certificate in this document). That said, you can start the toxssin server like this:

# python3 toxssin.py -u https://your.domain.com -c /your/certificate.pem -k /your/privkey.pem

Visit the project’s wiki for additional information.

XSS Exploitation Obstacles

In my experience, there are 4 major obstacles when it comes to Cross-Site Scripting attacks attempting to include external JS scripts:

the “Mixed Content” error, which can be resolved by serving the JavaScript payload via https (even with a self-signed certificate).
the “NET::ERR_CERT_AUTHORITY_INVALID” error, which indicates that the server’s certificate is untrusted / expired and can be bypassed by using a certificate issued by a trusted Authority.
Cross-origin resource sharing (CORS), which is handled appropriately by the toxssin server.
Content-Security-Policy header with the script-src set to specific domain(s) only will block scripts with cross-domain src from loading. Toxssin relies on the eval() function to deliver its poison, so, if the website has a CSP and the unsafe-eval source expression is not specified in the script-src directive, the attack will most likely fail (i’m working on a second poison delivery method to work around this).

Note: The “Mixed Content” error can of course occur when the target website is hosted via http and the JavaScript payload via https. This limits the scope of toxssin to https only webistes, as (by default) toxssin is started with ssl only.

How to get a Trusted Certificate

First, you need to own a domain name.

Register a domain for free

You can search for free options on freenom. It’s a bit tricky to do it correctly. I suggest you follow this instructional video. Also, if you create an account for the first time, make sure the Country you select matches your IP address or you might get errors.

Standard (paid) method

Purchase a domain from a registrar service (e.g. https://www.namecheap.com/). The most economic way is to search for a random string domain name (e.g. “fvcm98duf”) and check the less popular TLDs, like .xyz, as they will probably cost around 3$ per year.

Get a trusted certificate

After you purchase a domain name, you can use certbot (Let’s Encrypt) to get a trusted certificate in 5 minutes or less:

Append an A record to your Domain’s DNS settings so that it points to your server ip,
Follow certbots official instructions.

Tip: Don’t install and run certbot on your own, you might get unexpected errors. Stick with the instructions.

Changelog

2022-06-19 – Added the exec prompt command (you can now execute custom JS scripts against a session).
2022-06-23 – I added two simple, dirty scripts as templates for testing the exec prompt command. I also fixed the cmd prompt’s backward history access and made some improvements.