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Introduction:
Bug bounty hunting is not a lottery — it is a discipline of systematic reconnaissance, precise exploitation, and professional communication. In July, one hunter returned from a study-focused hiatus to achieve Top 8 in Brazil on HackerOne, submitting 2 Critical, 3 High, 1 Medium, and 2 Low valid bugs — and received a bonus from legendary triager Tommy DeVoss (Dawgyg) for report quality. This article deconstructs the methodology, tooling, and report-writing discipline that turns raw findings into recognized impact, offering a step‑by‑step framework for hunters at every level.
Learning Objectives:
- Master a repeatable reconnaissance-to-exploitation workflow for web and API targets.
- Understand how to prioritize vulnerability classes (Critical → Low) and structure reports for rapid triage.
- Learn practical Linux/Windows commands, tool configurations, and cloud hardening checks used in real-world bounties.
1. Reconnaissance: The Foundation of Every Bounty
Reconnaissance is where 80% of successful bug bounty outcomes are decided. Blind fuzzing without a map wastes time; disciplined asset discovery reveals the attack surface that scanners miss.
Step‑by‑step guide:
1.1 Subdomain Enumeration – Start with passive sources, then brute‑force with targeted wordlists.
Passive: gather from public datasets subfinder -d target.com -o subs.txt Active brute‑force with resolution and HTTP probing ffuf -u https://FUZZ.target.com -w /usr/share/wordlists/seclists/Discovery/DNS/subdomains-top1million-5000.txt -fc 400,404 -o active_subs.json
1.2 Live Host & Port Scanning – Verify which subdomains are alive and what services they expose.
Probe HTTP/HTTPS with httpx cat subs.txt | httpx -status-code -title -tech-detect -o live_hosts.txt Service scan with Nmap (stealthy) nmap -sS -sV -p- --min-rate 1000 -T4 -iL live_hosts.txt -oA nmap_scan
1.3 JavaScript & Endpoint Extraction – Modern SPAs leak API routes and secrets in client‑side JS.
Download JS files and extract endpoints
cat live_hosts.txt | waybackurls | grep ".js" | xargs -I{} curl -s {} | grep -Eo "(http|https)://[a-zA-Z0-9./?=_-]" >> endpoints.txt
Use gau for additional URL discovery
gau --subs target.com | grep -vE '.(css|png|jpg|jpeg|gif|ico|svg|woff|ttf|eot|pdf)' > urls.txt
1.4 Technology Fingerprinting – Identify frameworks, CMS, and server headers to tailor subsequent attacks.
whatweb -a 3 https://target.com
Windows alternative: Use PowerShell with `Invoke-WebRequest` and `Select-String` for basic endpoint harvesting, though the Linux toolchain remains superior for automation.
- Vulnerability Identification: From Low‑Hanging Fruit to Critical Impact
With a comprehensive asset map, you can now hunt systematically. The July results (2 Critical, 3 High, 1 Medium, 2 Low) reflect a balanced approach — not just chasing RCE, but also finding business‑logic flaws that carry high business impact.
Step‑by‑step guide:
2.1 Injection Testing (SQLi, Command Injection, SSTI)
Automated SQL injection with sqlmap (use with caution) sqlmap -u "https://target.com/product?id=1" --batch --level=3 --risk=2 Manual command injection test curl -X POST "https://target.com/ping" -d "ip=127.0.0.1; whoami"
2.2 Broken Access Control (IDOR, BOLA, Privilege Escalation) – Intercept requests and modify user identifiers.
– Burp Suite: Send requests to Repeater, change `user_id=123` to user_id=124, observe response.
– For APIs, test GraphQL endpoints with graphqlmap:
graphqlmap -u https://target.com/graphql -m dump
2.3 Business Logic Flaws – These often yield Medium/High findings. Test:
– Discount/ coupon abuse (negative values, repeated application)
– Rate‑limiting bypass (modify `X-Forwarded-For` headers)
– Step‑skipping in multi‑stage workflows (e.g., payment confirmation without prior steps)
2.4 Cloud Misconfigurations – A growing source of Critical findings.
Check for public S3 buckets aws s3 ls s3://target-bucket --1o-sign-request Scan Azure Blob containers az storage container list --account-1ame targetaccount --auth-mode login
Use ScoutSuite for comprehensive cloud posture assessments.
- The Art of the Report: Why Quality Earns Bonuses
Vinícius received a bonus from Tommy DeVoss (Dawgyg) for a low‑impact bug — purely because the write‑up was exceptional. In bug bounty, the report is your product. Triagers validate dozens of submissions daily; a clear, reproducible report cuts their time from minutes to seconds.
Step‑by‑step guide to a winning report:
3.1 – Be specific and impact‑focused.
> Bad: “IDOR vulnerability”
Good: “IDOR in `/api/v2/users/{id}/profile` Allows Full Account Takeover of Any User”
3.2 Steps to Reproduce – Provide a bullet‑point sequence that any triager can follow verbatim.
1. Log in as user A.
- Navigate to `https://target.com/api/v2/users/123/profile`.
3. Change `123` to `456` (user B’s ID).
4. Observe full PII and session tokens returned.
3.3 Expected vs. Actual Behavior – Clearly articulate the security failure.
– Expected: Returns 403 Forbidden or only public data.
– Actual: Returns full profile including email, phone, and password hash.
3.4 Proof of Concept (PoC) – Include a curl command or Burp request/response pair.
curl -X GET "https://target.com/api/v2/users/456/profile" -H "Authorization: Bearer <token_of_user_A>" -v
3.5 Impact & CVSS – Quantify business risk, not just technical severity. For the above IDOR:
– CVSS: 7.5 (High) – Confidentiality high, no user interaction.
– Business Impact: Full account takeover, data breach of all users.
3.6 Remediation Suggestion – Optional but appreciated: “Implement server‑side authorization checks using `@PreAuthorize` on the controller method.”
Pro Tip: Use Markdown formatting for readability. Front‑load severity in the title and introduction.
- Tooling Deep Dive: Burp Suite, FFUF, and Automation
Modern bug bounty relies on a curated toolchain. The July success likely involved Burp Suite for manual testing, FFUF for fuzzing, and custom scripts for automation.
Step‑by‑step guide:
4.1 Burp Suite Configuration
- Proxy: Set to
127.0.0.1:8080, install CA certificate in browser. - Intruder: Use for parameter fuzzing. Load wordlists from SecLists.
- Extensions: Install Autorize (for access control testing), JSON Web Tokens (for JWT analysis), and Turbo Intruder (for high‑speed fuzzing).
4.2 FFUF for Parameter Discovery
Fuzz GET parameters
ffuf -u https://target.com/page?FUZZ=test -w /usr/share/wordlists/param_names.txt -fc 400,404
Fuzz POST JSON bodies
ffuf -u https://target.com/api/login -X POST -H "Content-Type: application/json" -d '{"username":"admin","password":"FUZZ"}' -w /usr/share/wordlists/rockyou.txt -fc 401,403
4.3 Automation with Bash/Python
Loop through endpoints and check for common vulnerabilities
for url in $(cat endpoints.txt); do
curl -s -o /dev/null -w "%{http_code} %{url_effective}\n" "$url" | grep -v 200
done
Python script for header injection:
import requests
headers = {"X-Forwarded-For": "127.0.0.1", "User-Agent": "<?php system($_GET['cmd']); ?>"}
r = requests.get("https://target.com/debug", headers=headers)
print(r.text)
Windows PowerShell equivalent:
$urls = Get-Content .\endpoints.txt
foreach ($url in $urls) {
try { Invoke-WebRequest -Uri $url -Method Head -ErrorAction SilentlyContinue }
catch { Write-Host "Failed: $url" }
}
5. API Security: The New Frontier
Modern applications are API‑first. GraphQL, REST, and gRPC endpoints often expose larger attack surfaces than traditional web interfaces.
Step‑by‑step guide:
5.1 GraphQL Introspection – Many GraphQL endpoints leave introspection enabled.
query {
__schema {
types {
name
fields { name }
}
}
}
5.2 BOLA (Broken Object Level Authorization) – The API equivalent of IDOR.
– Intercept a request like GET /api/orders/123.
– Change `123` to 124, 125, etc., and check if other users’ orders are returned.
– Automate with Burp Intruder using a numeric payload list.
5.3 Rate‑Limit Bypass – APIs often enforce rate limits per IP. Bypass with:
– `X-Forwarded-For: 192.168.1.1` (iterate IPs)
– `X-Real-IP: 10.0.0.1`
– Use Turbo Intruder to rotate headers automatically.
5.4 Tool Recommendations
- Postman – for exploratory testing and collection exports.
- GraphQLmap – automated GraphQL security testing.
- API Hunter – AI‑powered discovery of business‑logic flaws.
6. Mitigation & Hardening: Thinking Like a Defender
Understanding how to fix vulnerabilities makes you a better hunter — and your remediation suggestions more credible.
Step‑by‑step guide for common fixes:
6.1 SQL Injection – Use parameterized queries (prepared statements).
// Java (JDBC) - Secure
PreparedStatement ps = conn.prepareStatement("SELECT FROM users WHERE id = ?");
ps.setInt(1, userId);
ResultSet rs = ps.executeQuery();
6.2 IDOR / BOLA – Implement server‑side access control for every object reference.
Django example
def get_order(request, order_id):
order = Order.objects.get(id=order_id)
if order.user != request.user:
raise PermissionDenied
return render(request, 'order.html', {'order': order})
6.3 Cloud Misconfigurations – Enforce least‑privilege IAM policies.
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Deny",
"Action": "s3:",
"Resource": "arn:aws:s3:::sensitive-bucket/",
"Condition": {
"Bool": {"aws:SecureTransport": "false"}
}
}
]
}
6.4 Rate Limiting – Implement on API gateways or middleware.
Nginx rate limiting
limit_req_zone $binary_remote_addr zone=api:10m rate=10r/s;
location /api/ {
limit_req zone=api burst=20 nodelay;
}
What Undercode Say:
- Discipline over talent: Vinícius’s month‑long study focus before hunting proves that structured learning — not raw luck — drives consistent results.
- Report quality is a force multiplier: A low‑impact bug with a stellar write‑up earned a bonus from a top triager. In competitive platforms, professionalism differentiates you from the crowd.
- Community matters: Acknowledging the Brazilian bug bounty community highlights that knowledge sharing and mentorship accelerate growth — especially for those without formal industry experience.
The July results (Top 8 Brazil, 2 Critical, 3 High, 1 Medium, 2 Low) are not an outlier; they are the output of a repeatable methodology. Vinícius’s journey — self‑taught, no formal experience, yet validated on world‑class targets — underscores that practical proof of skill outweighs credentials. His openness about seeking a first offensive security role is a call to action for hiring managers: talent exists outside traditional pipelines.
Prediction:
- +1 The demand for bug bounty hunters with strong report‑writing skills will increase as programs mature; platforms will introduce bonus structures specifically for report quality, not just severity.
- +1 AI‑assisted recon tools (e.g., API Hunter, Burp AI extensions) will lower the barrier to entry, enabling more hunters to find complex business‑logic flaws.
- -1 As automation grows, programs will tighten scope and require deeper manual testing, potentially reducing the volume of low‑hanging fruit available to newcomers.
- +1 Cloud misconfigurations will remain a top‑tier bounty source through 2026, with AWS, Azure, and GCP expanding their bug bounty scopes.
- -1 The increasing use of WAFs and API gateways will render basic injection attacks obsolete, forcing hunters to invest in advanced bypass techniques.
- +1 Community‑driven knowledge bases (like the HackerOne Community) will become essential for staying ahead of emerging vulnerability classes.
- +1 The “no formal experience” barrier will continue to erode as companies prioritize demonstrated skill over degrees — Vinícius’s story is a leading indicator of this shift.
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