Introduction

Web fuzzing is a technique used to discover security vulnerabilities in web applications by sending a wide range of unexpected or malformed inputs to various endpoints. This tutorial walks through the steps to set up a fuzzing target for effective web fuzzing, whether you're using tools like Penzzer, Burp Suite, or custom scripts.

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Prerequisites

Before setting up a fuzzing target, ensure you have:

• Basic knowledge of HTTP and web application architecture
• A local or test web server environment (e.g., Apache, Nginx, Node.js)
• Access to a fuzzing tool (Penzzer, ffuf, wfuzz, Burp Suite, etc.)
• A testable web application (e.g., DVWA, Juice Shop, a custom app)

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Step 1: Set Up a Test Web Application

For safety and legality, always fuzz in a controlled environment.

1. Choose a test application:
   • DVWA (Damn Vulnerable Web Application)
   • OWASP Juice Shop
   • A simple self-hosted Flask/Node app with endpoints
2. Install and configure:
   • Use Docker or a VM for isolation
   • Ensure the application is accessible via http://localhost or a specified IP

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Step 2: Identify Fuzzing Targets

Determine the parts of the web app to fuzz:

• URL endpoints (e.g., /search?q=...)
• Form fields and query parameters
• Cookies and headers (e.g., User-Agent, Referer)
• JSON and XML bodies in POST requests

Use tools like Burp Suite or browser dev tools to inspect HTTP traffic and enumerate possible fuzzing inputs.

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Step 3: Prepare Your Fuzzing Tool

Using ffuf

ffuf -u http://localhost:3000/search?q=FUZZ -w /path/to/wordlist.txt

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Using Penzzer (Example Configuration)

1. Create a new workspace
2. Select the Web module section
3. Pick what Testing Method you would like to use, either web path discovery, web API discovery, API endpoint testing, or GraphQL endpoint testing
4. Point Penzzer at the device under test (DUT) or web server
5. (Optionally) provide a list of URLs, endpoints, authentication mechanisms to be used
6. Click Test if you would like to verify the configuraition, or Start to just start with the test

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Step 4: Monitor and Analyze

• Monitor application logs and HTTP responses
• Look for anomalies: HTTP 500 errors, unexpected content, latency
• Use the fuzzing tool's output to prioritize and analyze potential findings

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Step 5: Validate and Triage Findings

Not every anomaly is a vulnerability. Manually validate interesting results:

• Reproduce the behavior with a browser or curl
• Check for indicators of XSS, SQLi, command injection, etc.
• Use additional tools (e.g., Burp Suite, sqlmap) for deeper analysis