Individual skill

business-logic-testing

Discover the application intended business rules and violate their assumptions - money and value manipulation, limit bypass, identity and relationship abuse, state misuse - proving persisted out-of-policy outcomes rather than status-code blips.

internal/tools/skills/data/application-security/business-logic-testing/SKILL.md

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Last checked
Nov 9, 2026

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Repository last updated
Nov 8, 2026
License
Apache-2.0

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# Business Logic Testing

## Purpose

Business logic flaws are rules the application MEANT to enforce but does not: prices, quantities, limits, coupons, quotas, identities, and states. Scanners cannot find them because the bug is not in a payload pattern - it is in the gap between intended rule and enforced rule. This skill teaches how to discover the intended rules black-box, then violate one assumption at a time and verify the backend actually persisted the out-of-policy outcome.

## Entry Conditions

- The application has any business rules: prices, quantities, coupons, credits, quotas, trials, referrals, invites, approvals, refunds, balances, votes, subscriptions
- You can perform at least one legitimate transaction to establish a baseline

## Step 1: Discover the Intended Rules

Black-box rule discovery from: UI copy ("one per customer", "limit 3", "non-refundable"), error messages on first violation (the app tells you the rule it thinks it enforces), pricing pages and ToS, how a legit transaction progresses (which fields are client-supplied vs recomputed), and client-side validation code (what the frontend refuses reveals what the backend SHOULD check).
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