Effective XSS methodology : The true way to hunt XSS

OK there no need to waste time, i will give you one liner to scan all subdomain then give them to my free API’s, and you can farm XSS without leaving your bed. Here it is :

echo "Why do you think there is such a thing like one liner XSS that can
conquer the world eh ? you lazy ass"

Before we dive into the nitty-gritty, let’s address a common misconception. You might have heard about some miraculous one-liner that scans all subdomains and finds XSS for you effortlessly. Well, sorry to burst your bubble, but there’s no such thing. Hunting for XSS requires a bit more effort than that. And yes, once again I encourage newcomers not to fall into the trap of looking for the ‘easy way’ to do bug bounty hunting.

First of all, you need to know what XSS is and how it can occur in the first place. This is an important part for newcomers who still have less familiarity with XSS. If you already have the knowledge, you can skip this part.

What is XSS ?

Cross-Site Scripting (XSS) is a type of security vulnerability typically found in web applications. It allows attackers to inject malicious scripts into content from otherwise trusted websites. When unsuspecting users visit these sites, the malicious scripts execute in their browsers, which can lead to various harmful outcomes such as data theft, session hijacking, and more.

Server based XSS

Server-based XSS vulnerabilities occur when the server-side code does not properly sanitize user inputs before reflecting them back to the client. These types of XSS include Reflected XSS and Stored XSS.

Client based XSS

Client-based XSS vulnerabilities occur when the client-side code does not properly sanitize or validate user inputs before inserting them into the DOM. This type of XSS is often referred to as DOM XSS.

Javascript framework and Why it change the way to hunt

A JavaScript framework is a collection of JavaScript code libraries that provide developers with pre-written code to use for routine programming tasks, essentially making the development of web applications more efficient and standardized. These frameworks provide a structured and organized way to build applications, promoting code reusability, maintainability, and scalability.

JavaScript frameworks like React, Angular, and Vue have revolutionized web development by promoting component-based architecture and encouraging the use of built-in security features that inherently protect against many common vulnerabilities, including XSS. These frameworks automatically escape and sanitize user input, reducing the risk of Reflected and Stored XSS. For example, React escapes data by default, and Angular has built-in sanitization mechanisms. However, they require developers to adhere to best practices and avoid dangerous functions like dangerouslySetInnerHTML in React or v-html in Vue without proper sanitization. This shift in development practices means that bug bounty hunters must now focus more on complex attack vectors, such as DOM-based XSS and vulnerabilities introduced through improper use of framework features, rather than traditional input validation flaws.

I’m not going to dig too deep into what XSS and JavaScript frameworks are, so I’ll provide you with a good resources to learn more about them :

My Research for XSS type possibility for Javascript FrameworkIdentify the Framework: The first step is to know what you are dealing with. Identify the framework the application uses, then move on to the next step. You can use the Wappalyzer extension in your browser to quickly identify the app’s infrastructure.Find Parameters or Behaviors that Reflect User Input: Look for parameters or behaviors that might reflect user input. If there are none, don’t waste time. Check areas like the profile section, comments, search functionalities, or hidden parameters.Check for Security Measures: Once you find reflecting behavior or parameters, check if they have security measures in place. The method varies depending on the context. For example, if the reflection is in an HTML attribute like <a href="your input">, you only need to check whether the double quotes are encoded or filtered. If they are, there's no need to fuzz with extensive XSS payloads. Move on to other parts or functionalities. If CSTI is possible, you can use {{7*7}} or other CSTI checks to see if the template is rendered.
For more on CSTI, refer to this resource: Client-Side Template Injection (CSTI).Determine if XSS is Possible: If the HTML input is rendered, check if you can execute JavaScript, such as using alert(). If you cannot execute JavaScript, check whether the server uses additional security measures like a Web Application Firewall (WAF) or Content Security Policy (CSP). You can then research how to bypass these security measures on the internet.

Here is the visualization of the methodology :

In conclusion, hunting for XSS vulnerabilities requires a methodical approach and a deep understanding of both server-based and client-based XSS. While JavaScript frameworks like React, Angular, and Vue offer built-in protections that mitigate many traditional XSS risks, they also introduce new challenges that require careful scrutiny. By identifying the framework, locating input reflection points, checking for security measures, and understanding how to bypass protections like WAFs and CSPs, you can effectively identify and exploit XSS vulnerabilities. Remember, there’s no one-liner solution to finding XSS — it demands persistence, creativity, and a thorough grasp of web security principles. Stay vigilant, keep learning, and always adhere to responsible disclosure practices.

Keep Learning !