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Akhileswara Reddy, a WIFI Penetration Tester and Application Security Engineer, recently uncovered a critical Insecure Direct Object Reference (IDOR) vulnerability, earning nearly five digits in £ through bug bounty programs. This flaw exposed unauthorized access to users’ sensitive Personally Identifiable Information (PII), including addresses, highlighting a major security risk.
You Should Know: Exploiting and Preventing IDOR Vulnerabilities
Understanding IDOR
IDOR occurs when an application provides direct access to objects (e.g., files, database entries) based on user input without proper authorization checks. Attackers manipulate parameters (e.g., user_id=12345) to access unauthorized data.
Exploiting IDOR – Manual Testing
- Intercept Requests – Use Burp Suite or OWASP ZAP to capture API calls.
Use cURL to test IDOR curl -X GET "https://example.com/api/user?id=12345" -H "Authorization: Bearer token123"
- Modify Parameters – Change `id` values to check if unauthorized access is possible.
3. Automate with Python –
import requests
for user_id in range(10000, 10005):
response = requests.get(f"https://example.com/api/user?id={user_id}", headers={"Authorization": "Bearer token123"})
if response.status_code == 200:
print(f"Data leaked for user {user_id}: {response.text}")
Preventing IDOR
- Implement Access Control – Use role-based checks before fetching data.
- Use Indirect References – Map user input to internal IDs via a secure middleware.
- Test with AuthZ Tools –
OWASP ZAP CLI for Auth Testing zap-cli quick-scan -s authz https://example.com/api
Bug Bounty Tips
- Look for API Endpoints – Check
/api/user,/profile/{id},/download?file=xyz. - Test Encoded/Hex IDs – Some apps use `base64` or UUIDs.
echo "12345" | base64 MTIzNDU=
What Undercode Say
IDOR remains a top web vulnerability due to weak server-side validation. Always:
– Enforce strict session validation –
Linux: Check open sessions (for server hardening) who -u
– Monitor logs for suspicious access –
Check Apache/Nginx logs for brute-force IDOR attempts
grep "GET /api/user?id=" /var/log/nginx/access.log | awk '{print $1}' | sort | uniq -c
– Use Windows ACLs – Restrict file access:
icacls C:\data\users.txt /deny "Everyone:(R)" Block unauthorized reads
Automate security with Linux hardening:
Fail2Ban rule for IDOR brute-forcing echo -e "[idor-attempt]\nenabled = true\nfilter = apache-idor\nlogpath = /var/log/apache2/access.log\nmaxretry = 3\nbantime = 3600" >> /etc/fail2ban/jail.local
Expected Output:
A secure system where:
- IDOR attempts are logged and blocked.
- Users’ PII remains inaccessible without proper authorization.
- Bug bounty hunters like Akhileswara continue to improve defenses.
Relevant URLs:
References:
Reported By: Akhileswarareddy With – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
