Mastering Advanced Web Application Exploitation Techniques for Bug Bounty Hunters
Bug bounty hunting has grown from a niche hobby to a full-fledged profession for many security enthusiasts. To stand out, you need more than just a basic understanding of vulnerabilities. This guide dives deep into advanced web application exploitation techniques that can help you uncover critical vulnerabilities and maximize your rewards.
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Why Focus on Advanced Techniques?
Basic vulnerabilities like XSS, SQL injection, and CSRF are still common, but the competition is fierce. By learning advanced techniques, you can target complex bugs that often go unnoticed, earn higher bounties, and become a sought-after bug hunter.
Here’s a curated list of advanced techniques and how to master them.
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1. HTTP Request Smuggling
Description: This vulnerability exploits the way front-end proxies and back-end servers parse HTTP requests.
How It Works:
Attackers send crafted HTTP headers (Content-Length or Transfer-Encoding) to manipulate request boundaries.
Example Payload:
POST / HTTP/1.1
Host: vulnerable.com
Content-Length: 48
Transfer-Encoding: chunked
0
GET /admin HTTP/1.1
Host: vulnerable.comTools:
Burp Suite’s HTTP Request Smuggling feature
Smuggler
Impact: Session hijacking, cache poisoning, or unauthorized access.
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2. Server-Side Template Injection (SSTI)
Description: Exploits occur when user input is rendered in server-side templates like Jinja2 (Python) or Twig (PHP).
How to Exploit:
1. Inject payloads to test if template code executes:
Jinja2: {{ 7*7 }}
Twig: {{ 7*7 }}
2. Escalate to RCE:
{{ ''.__class__.__mro__[1].__subclasses__()[40]('/bin/bash -c id',shell=True,stdout=-1).communicate() }}
Impact: Remote Code Execution (RCE), data theft, or server compromise.
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3. Server-Side Request Forgery (SSRF)
Description: Forces a server to make requests to internal or external systems on behalf of the attacker.
How to Exploit:
Test parameters accepting URLs:
?url=http://127.0.0.1/admin
Exploit internal services:
AWS Metadata: http://169.254.169.254/latest/meta-data/
Bypass Protections:
Use DNS rebinding or open redirect payloads.
Impact: Internal network scanning, data exfiltration, and firewall bypass.
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4. Advanced SQL Injection
Description: More sophisticated exploitation of SQL vulnerabilities, including time-based and second-order SQLi.
How to Exploit:
Time-Based Blind SQLi:
1 OR SLEEP(5)--
Second-Order SQLi: Inject malicious SQL during one process (e.g., registration) and trigger it in another (e.g., login).
Tools: SQLMap, Burp Suite.
Impact: Data theft, database modification, and privilege escalation.
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5. Insecure Deserialization
Description: Manipulates serialized data to inject malicious objects, leading to RCE or privilege escalation.
How to Exploit:
1. Identify serialized data in cookies, tokens, or hidden fields.
2. Generate malicious payloads with tools like ysoserial (Java) or PHPGGC.
Example:
O:8:"Exploit":2:{s:4:"file";s:10:"/etc/passwd";s:4:"data";s:3:"cat";}
Impact: RCE, privilege escalation, or data theft.
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6. Race Conditions
Description:
Exploiting concurrency issues in applications, such as redeeming the same voucher multiple times.
How to Exploit:
1. Identify endpoints that handle sensitive actions (e.g., fund transfers).
2. Send concurrent requests using Turbo Intruder or a custom Python script.
Example:
POST /redeem HTTP/1.1
coupon_code=FREE100
Impact: Financial loss, privilege escalation, or denial of service.
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7. JSON Web Token (JWT) Attacks
Description: Exploiting weaknesses in JWT implementations, such as improper algorithm validation.
How to Exploit:
None Algorithm:
Change the alg value to none and remove the signature.
{ "alg": "none", "typ": "JWT" }
Key Bruteforcing: Use tools like jwt_tool to brute-force signing keys.
Impact: Unauthorized access and privilege escalation.
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8. Web Cache Poisoning
Description: Manipulating cache mechanisms to serve malicious content.
How to Exploit:
Inject payloads into unkeyed inputs:
GET /?utm_source=<script>alert(1)</script>
Exploit cache headers (Cache-Control).
Impact: Persistent XSS or sensitive data exposure.
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Tools of the Trade
Recon: Subfinder, Amass, Assetfinder.
Exploitation: Burp Suite, Smuggler, SQLMap.
Automation: Python/Bash scripting.
Practice Labs: Hack The Box, TryHackMe, PortSwigger Academy.
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Advanced exploitation techniques require persistence, creativity, and practice. By mastering these, you can uncover higher-severity bugs, stay ahead of the competition, and significantly boost your earnings.
Keep learning, stay ethical, and happy hunting!
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