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Reflected XSS into a JavaScript string single quote and backslash escaped (مستوي متوسط) - Bug Bounty

Introduction

In this lesson focused on intermediate bug bounty techniques, we explore how to exploit a reflected Cross-Site Scripting (XSS) vulnerability, specifically when dealing with search queries in a web application. The challenge presented is that input sanitization forbids the use of single quotes and backslashes, which can create a layer of protection against XSS attacks. However, this does not eliminate the possibility of executing JavaScript.

Understanding the Vulnerability

The vulnerability arises from the ability to send a search query that gets processed and reflected back onto the page. In this case, using tools like Burp Suite can help us capture and replay our web requests to test for XSS. By manipulating the input, we can craft a payload that exploits this vulnerability.

Utilizing Burp Suite

To begin the exploitation process, we can use the Burp Suite’s proxy tool. By sending a search query with a specific payload, we can then inspect the history of our requests using the HTTP history tool. This allows us to identify our input, how it gets reflected on the page, and whether it appears in JavaScript code.

Crafting the Payload

Upon understanding the page output, we recognize that even though single quotes and backslashes are disallowed, we can still use angles brackets or other characters to craft a functioning payload. For instance, by creatively closing the existing script tag in the output and opening a new one, we can introduce our own JavaScript code.

Here’s how the payload can be structured:

  1. Close the original script tag.
  2. Introduce a new <script> tag.
  3. Inside the new script, we can place JavaScript functions, such as alert(), to confirm the execution of our code.

Implementation Steps

  1. In the search input, close the existing script tag.
  2. Open a new script tag.
  3. Insert the JavaScript command (e.g., alert('XSS!')).
  4. Submit the search query.

After submitting, if implemented successfully, the alert function should execute, confirming that our JavaScript code is running on the page.

Conclusion

This lesson taught us a valuable lesson about recognizing and exploiting XSS vulnerabilities, even with certain constraints like disallowed characters. The ability to think outside the box and approach problems from different angles makes a skilled bug bounty hunter. Practice and exposure to various vulnerabilities will enhance your skills and prepare you for real-world scenarios.

I encourage everyone to keep experimenting and learning, as each challenge brings new insights. If there are any questions or thoughts, feel free to leave them in the comments. Until next time, let's pray for knowledge that benefits us.

Keywords

  • Reflected XSS
  • JavaScript
  • Search Query
  • Burp Suite
  • Payload Crafting
  • Script Tag
  • Web Application Security

FAQ

Q1: What is reflected XSS?
A1: Reflected XSS is a type of vulnerability where an attacker can inject malicious scripts into a web application, which are then reflected back to the user in real-time.

Q2: How does Burp Suite help in finding XSS vulnerabilities?
A2: Burp Suite is a web application security testing tool that allows users to intercept, inspect, and modify web requests. It helps in capturing input and observing how the application responds, making it easier to identify potential XSS vulnerabilities.

Q3: What should I do if the web application sanitizes certain characters?
A3: If certain characters like single quotes or backslashes are sanitized, you can try using alternative characters or methods, such as closing existing HTML tags and opening new ones, to introduce your payload.

Q4: Is it safe to test XSS vulnerabilities on real websites?
A4: No, it is illegal and unethical to test XSS vulnerabilities on websites without permission. Always use designated testing environments or obtain explicit authorization before testing any systems.

Q5: How can I improve my skills in exploiting web vulnerabilities?
A5: Practice on platforms like Hack The Box, PortSwigger Web Security Academy, and other CTF (Capture The Flag) challenges to enhance your skills in identifying and exploiting web vulnerabilities systematically.

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