How I Earned on Bugcrowd Using DuckDuckGo Dorks to Find 2x Reflected XSS + Video

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Introduction:

Reconnaissance is the cornerstone of any successful bug bounty hunt. While Google dorks are a staple for finding exposed vulnerabilities, limiting your search to a single engine can leave low-hanging fruit untouched. By leveraging alternative search engines like DuckDuckGo with specialized dorks, security researchers can discover overlooked endpoints and parameter vectors, leading to high-impact findings such as reflected cross-site scripting (XSS).

Learning Objectives:

  • Understand how to utilize DuckDuckGo dorks for effective bug bounty reconnaissance.
  • Learn the methodology for identifying and testing for reflected XSS vulnerabilities.
  • Master the use of specialized search operators to uncover hidden or forgotten web application endpoints.

You Should Know:

  1. Expanding the Attack Surface with Alternative Search Engines

While Google is the industry standard for dorking, it is not the only index of the internet. DuckDuckGo, known for its privacy focus, often indexes pages and parameters that Google may deprioritize or filter out. For bug bounty hunters, this creates a unique opportunity. The core principle remains the same: using search operators to locate specific strings, file types, or URL structures that indicate a potential vulnerability.

The post highlights a successful $xxxx payout for two reflected XSS vulnerabilities discovered using this method. The key was shifting from the common “Google dorks” mindset to “DuckDuckGo dorks,” utilizing the same logic but on a different data set. This approach forces the hunter to look beyond the first page of search results and into the long-tail data that other researchers might miss.

Step‑by‑step guide:

  1. Identify the Target: Define the scope of your bug bounty program (e.g., .target.com).
  2. Craft Your Dork: Use DuckDuckGo’s search bar with standard operators. Focus on parameters known to be vulnerable to XSS.

Basic: `site:.target.com inurl:q=`

Parameter Focus: `site:.target.com inurl:?search=`

File Type: `site:.target.com filetype:php inurl:?id=`

  1. Analyze Results: Look for URLs with parameters like q=, s=, id=, page=, or redirect=. These are common injection points.
  2. Verify Accessibility: Ensure the discovered endpoints are in scope and actively accessible. Use `curl` to confirm the page returns a 200 OK status and contains the reflected parameter.
 Linux / macOS / WSL
curl -s "https://target.com/search?q=test123" | grep "test123"

 Windows PowerShell
Invoke-WebRequest -Uri "https://target.com/search?q=test123" | Select-Object -ExpandProperty Content | Select-String "test123"

2. Crafting and Executing XSS Payloads

Once you have identified a parameter that reflects user input back into the page source, the next step is to test for XSS. The goal is to break out of the HTML context and execute JavaScript. The most basic and effective test is the simple alert payload. However, in a professional bug bounty context, you must prove impact without causing damage. A simple `alert(1)` is sufficient to demonstrate the vulnerability.

The process involves sending a payload to the parameter and observing if it executes in the browser. If the application sanitizes special characters like <, >, or ", you may need to try different contexts (e.g., inside HTML tags, inside JavaScript strings, or within event handlers).

Step‑by‑step guide:

  1. Inject a Test String: Append a unique string to your target parameter. For example: `https://target.com/search?q=UNDERCODE-XSS-TEST`.
  2. Check Reflection: View the page source (Ctrl+U) and search for your unique string. Note where it appears—inside an HTML tag, a JavaScript block, or an attribute.
  3. Deploy Basic Payload: Based on the context, try a simple payload.
    HTML Context: `https://target.com/search?q=`
    Attribute Context: `https://target.com/search?q=”>`
    JavaScript Context: `https://target.com/search?q=test’;alert(1);//`
    4. Automate Testing with a Tool: For efficiency, use a tool like `ffuf` to fuzz parameters with a list of XSS payloads. This is especially useful if the vulnerability is behind a login or requires specific cookies.
 Using ffuf to fuzz a parameter with XSS payloads
ffuf -u "https://target.com/search?q=FUZZ" -w /path/to/xss_payloads.txt -c -ac -H "Cookie: session=YOUR_SESSION_COOKIE"

3. Understanding the DuckDuckGo Advantage

The success of this technique lies in the differences in search engine indexing. Google heavily filters “spammy” parameters and often de-indexes pages with excessive query strings to improve user experience. DuckDuckGo, however, often retains these parameters, making it a goldmine for finding developer endpoints, test pages, and legacy applications that are not visible on Google. This includes pages with parameters like debug=true, test=1, or `admin=yes` that may have been overlooked during the deployment process.

Furthermore, DuckDuckGo does not personalize search results based on a user’s history to the same extent as Google. This allows for a more neutral and comprehensive view of the indexed content, ensuring that you are not missing critical results due to algorithmic filtering.

Step‑by‑step guide:

  1. Combine Operators: Use a combination of operators to narrow results.

`site:target.com intitle:”test” inurl:?id=`

`site:target.com intext:”error” inurl:?debug=`

  1. Leverage Filetype Dorks: Search for configuration or log files.

`site:target.com filetype:log`

`site:target.com filetype:sql inurl:backup`

  1. Explore Subdomains: Use `site:.target.com` to discover all indexed subdomains. You can then use `subfinder` or `assetfinder` to automate this discovery and compare the results with DuckDuckGo’s index for hidden gems.
 Using subfinder to enumerate subdomains, then using the results for dorking
subfinder -d target.com -silent | tee subdomains.txt
 Now manually search DuckDuckGo for each subdomain
 Example: site:admin.target.com inurl:?page=

4. Advanced Payload Obfuscation for WAF Bypass

In many modern web applications, a Web Application Firewall (WAF) may block basic XSS payloads like <script>alert(1)</script>. To successfully demonstrate impact and earn a bounty, you may need to bypass these filters. This involves encoding payloads, using alternative HTML tags, or leveraging JavaScript events.

For reflected XSS, the key is to ensure the payload reaches the browser in a form that the WAF does not recognize as malicious, but that the browser will still parse and execute. This is a cat-and-mouse game that requires creativity and a deep understanding of HTML and JavaScript parsing.

Step‑by‑step guide:

  1. Test Filter Detection: Start by injecting a harmless but potentially blocked string like `