Overlooked Reconnaissance Techniques for Bug Bounty Hunters

Bug bounty hunting is a game of creativity, patience, and persistence. While most hunters focus on common recon techniques such as subdomain enumeration, port scanning, and directory brute-forcing, many overlook more advanced and unconventional methods that can reveal hidden assets and security vulnerabilities. This guide explores overlooked reconnaissance techniques that can help bug bounty hunters gather valuable data and find security flaws that others might miss.

1. Using Targeted Wordlists

One of the biggest mistakes bug bounty hunters make is relying solely on default wordlists. Custom and targeted wordlists, tailored to the specific technologies, applications, and industry of the target, can significantly improve enumeration results. Consider the following approaches:

• Extract keywords from the company’s website, repositories, and past disclosures.
• Generate wordlists from GitHub repositories and documentation.
• Use tools like cewl to create lists from website content.
• Leverage existing lists from previous bug reports and asset mappings.

2. Virtual Host Enumeration

Virtual host enumeration helps uncover hidden applications running on the same server that might not be listed in DNS records. Some effective methods include:

• Using ffuf or gau with a list of potential subdomains.
• Querying certificates from sources like crt.sh.
• Utilizing tools like hosthunter to identify virtual hosts.
• Checking for alternate virtual hosts via VHostScan.

3. Forced Browsing with Different HTTP Methods

Web servers and APIs often handle HTTP methods differently. Many hunters only check for GET and POST requests, but testing additional methods like OPTIONS, PUT, DELETE, PATCH, TRACE, and CONNECT can reveal misconfigurations or unintended behavior.

• Use curl -X METHOD or Burp Suite to test HTTP method support.
• Exploit misconfigured methods to access restricted resources.
• Identify unintended behavior by sending crafted payloads.

4. JavaScript File Monitoring

JavaScript files often contain crucial information such as API keys, endpoints, and internal logic. Instead of passively reviewing JS files, actively monitor them for changes.

• Use jsbeautifier to format and analyze obfuscated scripts.
• Monitor changes over time using tools like waybackurls.
• Extract endpoints and parameters dynamically with LinkFinder.

5. Crawling with Different User-Agent Headers

Some web applications display different content or behaviors depending on the user-agent header. Testing with different user-agents can reveal:

• Admin panels or debugging endpoints.
• Mobile-only or legacy versions of the website.
• Hidden features enabled for specific browsers.

Tools like gobuster and wfuzz allow setting custom user-agents to simulate different environments.

6. Finding Related Assets with Favicon Hashes

Organizations often host related assets on different subdomains or infrastructure. By analyzing favicon hashes, bug hunters can identify linked services:

• Extract the favicon’s hash using fav-up or shodan.
• Use services like Shodan to find servers with the same favicon.
• Correlate discovered hosts with known company assets.

7. Looking Up Legacy Versions of JavaScript Files

Historical versions of JavaScript files can contain references to deprecated API endpoints, sensitive data, or old configurations.

• Use the Wayback Machine (waybackurls) to find previous JS versions.
• Compare old and new files to spot changes in authentication logic.
• Extract API endpoints and deprecated routes.

8. Extracting Subdomains from SSL Certificates

SSL certificates often contain information about multiple subdomains linked to the same organization. Services like crt.sh allow searching for SSL certificates issued to a domain.

• Query crt.sh with SELECT DISTINCT name_value FROM certificate WHERE name_value LIKE '%.example.com'.
• Use tools like Certspotter and Subfinder for automated enumeration.
• Extract organization names from certificate details.

9. Leveraging Cloud Asset Enumeration

Many organizations use cloud services like AWS, Google Cloud, and Azure. Enumerating cloud-based assets can uncover misconfigured storage buckets, API endpoints, and exposed credentials.

• Use tools like S3Scanner, CloudBrute, and GCPBucketBrute.
• Identify exposed storage by testing common naming conventions.
• Check for public API gateways and Lambda functions.

10. Discovering Hidden Endpoints via Referrer Headers

Monitoring Referer headers from HTTP responses can reveal internal URLs, API endpoints, and third-party integrations.

• Intercept traffic using Burp Suite to analyze Referer headers.
• Look for URLs leading to admin panels or staging environments.
• Use custom scripts to extract and monitor Referer headers dynamically.

Conclusion

Reconnaissance is the foundation of bug bounty hunting. While traditional techniques are effective, combining them with overlooked methods like targeted wordlists, virtual host enumeration, favicon hash analysis, and legacy JavaScript monitoring can significantly increase your chances of discovering vulnerabilities. By continuously refining and expanding reconnaissance strategies, bug bounty hunters can stay ahead of the curve and uncover security weaknesses before malicious actors do.