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Introduction:
The world of Bug Bounty programs offers a unique battleground where ethical hackers and security researchers can test their mettle against real-world applications. Unlike simulated lab environments, bug bounty hunting involves dissecting live systems, often with massive user bases, to uncover hidden flaws before malicious actors do. This field requires a blend of meticulous reconnaissance, deep technical knowledge of web vulnerabilities, and the perseverance to document findings professionally. The journey of a bug hunter is defined by consistent progress, where small, daily discoveries build the expertise needed to identify critical, high-paying vulnerabilities.
Learning Objectives:
- Understand how to establish a repeatable and effective bug hunting methodology based on reconnaissance and logic analysis.
- Learn to identify and exploit common web vulnerabilities such as IDOR, XSS, and SQLi in live environments.
- Master the art of writing clear, concise, and actionable vulnerability reports that lead to faster validation and bounties.
You Should Know:
- Phase 1: Reconnaissance – The Foundation of Every Discovery
Before firing off automated scanners, professional bug hunters spend hours mapping the target’s digital footprint. This involves discovering subdomains, hidden endpoints, and technologies in use. A tool like `ffuf` (Fuzz Faster U Fool) is indispensable for content discovery, while `httpx` helps filter live hosts.
Step‑by‑step guide on using ffuf for directory brute-forcing:
Install ffuf (if not already installed) go install github.com/ffuf/ffuf@latest Basic directory fuzzing against a target URL Use a common wordlist like /usr/share/wordlists/dirb/common.txt ffuf -u https://target.com/FUZZ -w /path/to/wordlist.txt -fc 403,404 Explanation: -u : The target URL. The keyword FUZZ tells ffuf where to insert the payload. -w : Path to your wordlist. -fc : Filter out HTTP status codes (like 403 Forbidden or 404 Not Found) to reduce noise. This command reveals hidden directories and files that are not linked on the main site.
- Phase 2: Logic Flaw Hunting – The Art of IDOR
Insecure Direct Object References (IDOR) remain one of the most lucrative bug classes. They occur when an application exposes a direct reference to an internal object (like a file or database key) without proper access control checks. This requires manual testing and parameter manipulation.
Step‑by‑step guide on testing for IDOR:
- Intercept Traffic: Use Burp Suite (Community Edition is fine) to intercept requests after logging into your account (User A).
- Identify Reference: Look for requests containing identifiers like
user_id=1234,invoice=5678.pdf, or/api/v1/users/me. - Modify the Request: Send the request to Burp Repeater. Change the identifier to a value belonging to another user (e.g.,
user_id=1235). You can find these IDs by creating another account (User B) or by scraping public profiles. - Forward and Analyze: Forward the modified request. If the server responds with User B’s private data (like personal details, private messages, or invoices) while you are still logged in as User A, you have found a valid IDOR vulnerability.
- Escalate: Try changing the HTTP method (GET to POST) or adding parameters to see if you can modify data belonging to other users.
3. Phase 3: Exploitation – Chaining Vulnerabilities
Sometimes a low-severity issue can be chained with another to create a critical impact. For example, a Reflected Cross-Site Scripting (XSS) vulnerability might seem trivial, but if combined with a CSRF (Cross-Site Request Forgery) flaw, it could lead to account takeover.
Step‑by‑step guide on testing for Reflected XSS:
- Find Input Vectors: Identify any part of the application that reflects user input back in the response, such as search bars, error messages, or URL parameters.
- Inject Payloads: Start with simple, non-executable payloads to confirm reflection, like
'"><h1>Test</h1>. - Craft Proof-of-Concept: If you see your HTML tags reflected unsanitized, inject a standard JavaScript PoC to demonstrate impact.
<script>alert('XSS Found')</script> - Encode for Filters: If basic payloads are blocked, try context-specific encoding. For example, in a JavaScript variable context:
';alert('XSS')//
Windows Command Equivalent (for testing local file inclusion):
While XSS is browser-based, testing local file inclusion on a server might involve:
Using curl on Windows to test for path traversal curl "http://target.com/view?file=..\..\..\windows\win.ini" Or for Linux-based servers curl "http://target.com/view?file=../../../../etc/passwd"
- Phase 4: Reporting – Turning a Bug into a Bounty
A vulnerability is only worth its bounty if the triage team can understand and reproduce it. A well-written report is clear, concise, and provides a clear impact.
Step‑by‑step guide on structuring a professional report:
- Be specific, e.g., “IDOR on `/api/user/details` allows unauthorized viewing of any user’s PII” instead of “Broken Access Control.”
- Summary: Briefly describe the endpoint’s purpose and the flaw.
3. Steps to Reproduce:
- Step 1: Log in as User A and navigate to the account settings.
- Step 2: Open Burp Suite and intercept the request to
/api/user/details. - Step 3: Change the `user_id` parameter from `1111` to
2222. - Step 4: Forward the request.
- Step 5: Observe the response containing User B’s email address and phone number.
- Impact: Clearly state the worst-case scenario. “This vulnerability allows an attacker to exfiltrate the PII of every user on the platform, leading to privacy violations and potential account takeovers.”
- Proof of Concept (PoC): Include a screenshot of the request in Burp Repeater and the server’s response showing the leaked data. For XSS, a screenshot of the alert box is standard.
5. Phase 5: Automation and Workflow on Windows
While many tools are Linux-native, Windows users can leverage WSL (Windows Subsystem for Linux) to run the same toolchains, or use native PowerShell scripts for automation.
Step‑by‑step guide on setting up a simple recon loop in PowerShell:
Define your target domain
$domain = "target.com"
Use a tool like subfinder (if installed via WSL) but for pure PowerShell,
we can use certificates to find subdomains (a common passive technique).
Fetch certificate transparency logs
$url = "https://crt.sh/?q=%25.$domain&output=json"
$response = Invoke-RestMethod -Uri $url -Verbose
Extract unique subdomains
$subdomains = $response | ForEach-Object { $_.name_value } | Sort-Object -Unique
Output the subdomains to a file
$subdomains | Out-File -FilePath "subdomains_$domain.txt"
Write-Host "[+] Found $($subdomains.Count) subdomains for $domain"
This passive recon step is safe and identifies all publicly logged subdomains.
What Undercode Say:
- Consistency Over Intensity: As Muhammad Rizky Firdaus highlights, the key to success in bug bounty is not waiting for a big breakthrough, but making consistent, daily progress. Each small test, each logged bug, builds an intuition that automated scanners cannot replicate.
- Validation is Key: The emotional rollercoaster of having bugs validated (“mantap”) or rejected (“kurang mantap”) is part of the learning curve. Every report, whether accepted or not, provides feedback that refines a hunter’s methodology and understanding of a program’s scope.
- The post underscores that bug bounty hunting is a marathon, not a sprint. The technical skills to find vulnerabilities are only half the battle; the other half is the discipline to document them thoroughly and the resilience to keep hunting even after setbacks. This field uniquely blends technical penetration testing with the soft skills of communication and persistence, making it one of the most dynamic careers in cybersecurity.
Prediction:
As AI-powered code generation becomes more prevalent, we will likely see a surge in logic-based vulnerabilities. While AI can help prevent simple syntax errors and injection flaws, it struggles with complex business logic and authentication bypasses. Future bug bounty hunters will pivot from simple XSS and SQLi to deeply chained exploits that abuse the intended functionality of an application in unexpected ways, making the human element in security testing more critical than ever.
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Reported By: Muhammad Rizky – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
