From LinkedIn Celebration to Payday: How I Hacked Spacelift and Cashed Out on Critical IDOR & Access Control Flaws + Video

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Introduction:

In the competitive realm of bug bounty hunting, uncovering critical vulnerabilities in modern tech stacks is the ultimate validation for a security researcher. A recent success story involves the discovery of Insecure Direct Object Reference (IDOR) and broken Access Control vulnerabilities within Spacelift, a prominent infrastructure as code management platform, leading to a substantial monetary reward via the YesWeHack platform. This case study dissects the technical journey from reconnaissance to exploitation, providing a blueprint for understanding and testing these pervasive authorization flaws.

Learning Objectives:

  • Understand the fundamental mechanics and dangerous implications of IDOR and Broken Access Control vulnerabilities in modern web applications and APIs.
  • Learn a proven, methodical approach for testing authorization layers, including endpoint analysis, parameter manipulation, and privilege escalation techniques.
  • Acquire practical skills for crafting proof-of-concept exploits and implementing robust mitigation strategies to defend your own applications.

You Should Know:

  1. Deconstructing the Attack Surface: IDOR & Access Control
    At their core, IDOR and Broken Access Control are failures in authorization. An IDOR occurs when an application uses user-supplied input (like an object ID in a URL or API request) to access an object directly without proper verification that the user is authorized for that object. Broken Access Control is a broader category (ranked 1 in the OWASP Top 10 2021) where restrictions on what authenticated users are allowed to do are not properly enforced.

Step‑by‑step guide:

  1. Mapping Authenticated Sessions: After logging into a target application (e.g., app.spacelift.io), use browser developer tools (F12) to monitor network traffic. Filter for XHR/Fetch requests.
  2. Identifying Object References: Look for API calls that include predictable parameters like userId, accountId, fileId, orderId, projectId. Common patterns are `/api/v1/user/12345/profile` or GET /api/invoices?user=6789.
  3. Baseline Establishment: Document the normal, authorized requests and their responses for your low-privilege test account.

2. The Art of Parameter Manipulation and Testing

This phase involves actively manipulating the identified parameters to test for authorization bypasses.

Step‑by‑step guide:

  1. Tool Selection: Use Burp Suite Repeater, OWASP ZAP, or even browser extensions like `ModHeader` for API testing.
  2. Sequential Testing: For a found endpoint /api/project/{id}/config, change the `{id}` value incrementally (e.g., 1001, 1002). Use simple scripts to automate enumeration. 
    Example curl loop for IDOR testing
for id in {1000..1050}; do
echo "Testing ID: $id"
curl -H "Authorization: Bearer $YOUR_TOKEN" https://api.target.com/v1/secret/$id
echo "\n"
done
  3. Horizontal vs. Vertical Escalation: Test for horizontal escalation (accessing another user’s data of the same privilege) by swapping numeric IDs. Test for vertical escalation by accessing endpoints or parameters reserved for higher roles (e.g., admin=true, role=administrator).

3. Exploiting Contextual IDOR in API Endpoints

Modern applications often use complex APIs where object references may be nested or non-sequential.

Step‑by‑step guide:

  1. Analyze POST/PUT Requests: Don’t just test GET requests. If you can create an object (e.g., a new ticket POST /api/tickets), the response may contain a new object ID. Immediately try to `GET /api/tickets/{new_id}` from a different user’s context.
  2. Test UUIDs: Even Globally Unique Identifiers (UUIDs) can be vulnerable if they are exposed elsewhere in the application (e.g., in a shared document link). Capture a UUID from a legitimate, authorized request and attempt to use it in another user’s session.
  3. Mass Assignment & Parameter Pollution: Sometimes, vulnerabilities arise from binding user input directly to internal objects. Test by adding unexpected parameters to requests. 
    POST /api/user/update HTTP/1.1
Host: target.com
{"name":"attacker", "email":"[email protected]", "role":"admin", "account_id":4321}

  4. Windows & Linux Command-Line Recon for Bug Bounty
    Effective hunting starts with reconnaissance to discover endpoints and subdomains that may harbor flawed logic.

Step‑by‑step guide:

1. Subdomain Enumeration:

 Using subfinder and amass (Linux)
subfinder -d spacelift.io -o subs.txt
amass enum -d spacelift.io -o subs_amass.txt
sort -u subs.txt > all_subs.txt

2. Port and Service Discovery: Probe for exposed management interfaces.

 Using naabu
naabu -l all_subs.txt -top-ports 1000 -o naabu_results.txt

3. Wayback Machine & Archive Enumeration: Gather historical endpoints.

 Using waybackurls
echo "spacelift.io" | waybackurls > urls.txt
cat urls.txt | grep "api|token|id|user|admin" > sensitive_endpoints.txt

5. Building a Proof-of-Concept (PoC) for Reporting

A clear, reproducible PoC is critical for a valid bug bounty report and swift remediation.

Step‑by‑step guide:

  1. Document Steps: Write a clear narrative: “As User A ([email protected]), I performed steps X, Y, Z to access the resource of User B ([email protected]).”
  2. Capture Evidence: Use screenshots, full HTTP request/response cycles from Burp Suite, and video recordings.
  3. Craft the Exploit Code: Provide a simple script that demonstrates the flaw. 
    import requests</li>
</ol>

attacker_token = 'ATTACKER_JWT_TOKEN'
victim_resource_id = 'VICTIM_OBJECT_ID'
target_url = f'https://api.target.com/data/{victim_resource_id}'

headers = {'Authorization': f'Bearer {attacker_token}'}
response = requests.get(target_url, headers=headers)

if response.status_code == 200:
print(f"[+] Success! Accessed victim data: {response.text[:500]}")
else:
print(f"[-] Failed. Status: {response.status_code}")

    6. Mitigation Strategies: Secure Coding Practices

    To prevent these flaws, developers must implement authorization checks on every request.

    Step‑by‑step guide:

    1. Implement Access Control Checks: Use a centralized access control routine. Never rely on obfuscated or client-side controls. 
      // Node.js/Express Example Middleware
const checkResourceOwner = async (req, res, next) => {
const resourceId = req.params.id;
const userId = req.user.id;</li>
</ol>

const resource = await db.Resource.findByPk(resourceId);
if (!resource || resource.ownerId !== userId) {
return res.status(403).json({ error: 'Forbidden' });
}
next();
};
app.get('/api/resource/:id', checkResourceOwner, getResourceHandler);

      2. Use Indirect Reference Maps: Avoid using sequential integers. Use random, unpredictable UUIDs as public references, mapped internally to real objects via a server-side lookup table.
      3. Adopt Role-Based Access Control (RBAC): Define roles and permissions clearly, and enforce them consistently across all API endpoints and UI flows.

      7. Integrating into a Continuous Security Workflow

      Security is not a one-time test. Integrate checks for authorization flaws into your SDLC.

      Step‑by‑step guide:

      1. Static Application Security Testing (SAST): Use tools like Semgrep, CodeQL, or Checkmarx to find patterns of missing authorization in code. 
        Example Semgrep rule pattern for potential IDOR
semgrep --config "p/python" --pattern "$ID = request.GET.get('id'); ... Model.objects.get(id=$ID)" /path/to/code
      2. Dynamic Testing with Automated DAST: Configure tools like OWASP ZAP or Burp Suite Enterprise to run authenticated scans, testing for access control issues across user roles.
      3. Regular Penetration Testing: Schedule periodic, professional penetration tests and encourage responsible disclosure through a bug bounty program.

      What Undercode Say:

      • The Human Element is Key: This success underscores that beyond automated tools, critical flaws are found by understanding business logic, experimenting with user flows, and thinking like an adversary. Mentorship, as acknowledged in the post, dramatically accelerates this skill development.
      • Authorization is a Core Pillar: The recurrence of IDOR/Broken Access Control as top vulnerabilities highlights a systemic issue in development prioritization. Security must shift-left, with developers receiving robust training in secure authorization design patterns from day one.

      The technical journey from a congratulatory LinkedIn post to the underlying hack reveals a classic yet high-impact security oversight. The researcher’s systematic approach—endpoint discovery, parameter manipulation, and contextual exploitation—turned a theoretical vulnerability into a tangible reward. This case is not an anomaly but a reflection of the constant chasm between perceived and actual authorization enforcement in complex applications.

      Prediction:

      The future of these vulnerabilities will evolve alongside technology stacks. We will see a rise in IDOR-like flaws in GraphQL APIs (through insecure node field access), within serverless function architectures (misconfigured event triggers), and in complex microservice communications where authentication context is lost. Mitigation will increasingly rely on standardized, policy-as-code frameworks like Open Policy Agent (OPA) and integrated security platforms that provide unified authorization layers across diverse services. However, the human-driven, creative testing methodology demonstrated here will remain indispensable, as automation alone cannot yet fully replicate the contextual reasoning required to chain logic flaws into a critical exploit.

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      Reported By: Nour Ammar – Hackers Feeds
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