# Sast Businesslogic

Detect business logic vulnerabilities in a codebase using a three-phase approach...

- Repository: https://github.com/utkusen/sast-skills (1357 stars)
- Category: Security
- License: MIT
- Last updated: 2026-10-23
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add utkusen/sast-skills --skill sast-businesslogic -g -a claude-code -y`
Codex: `npx skills add utkusen/sast-skills --skill sast-businesslogic -g -a codex -y`
Cursor: `npx skills add utkusen/sast-skills --skill sast-businesslogic -g -a cursor -y`
Gemini CLI: `npx skills add utkusen/sast-skills --skill sast-businesslogic -g -a gemini-cli -y`

## Description

Detect business logic vulnerabilities in a codebase using a three-phase approach: threat modeling (domain analysis and attack scenarios), batched verify (check exploitable gaps in parallel subagents, 3 scenarios each), and merge (consolidate batch results). Covers price manipulation, workflow bypass, limit violations, race conditions, reward abuse, etc. Requires sast/architecture.md (run sast-analysis first). Outputs findings to sast/businesslogic-results.md. Use when asked to find business logic, logic flaws, or abuse-of-function bugs.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Business Logic Vulnerability Detection

You are performing a focused security assessment to find business logic vulnerabilities in a codebase. This skill uses a three-phase approach with subagents: **threat modeling** (understand the domain and generate attack scenarios), **batched verify** (check whether scenarios are exploitable in parallel batches of 3), and **merge** (consolidate batch results).

**Prerequisites**: `sast/architecture.md` must exist. Run the analysis skill first if it doesn't.

---

## What are Business Logic Vulnerabilities

Business logic vulnerabilities arise when an application's intended workflow, rules, or constraints can be manipulated to produce unintended outcomes, without exploiting technical flaws like injection or memory corruption. The attacker operates within the application's own features but uses them in ways the developers did not anticipate.

The core pattern: *the application accepts input that is syntactically valid and passes authentication/authorization, but violates a business rule that was never enforced in code.*

### What Business Logic Vulnerabilities ARE

- Submitting a negative quantity to a purchase endpoint, receiving a credit instead of a charge
- Applying the same one-time discount coupon multiple times in parallel requests
- Skipping the payment step in a multi-step checkout by replaying a later step's request
- Posting a rating of 9999 to a movie rating endpoint that should cap ratings at 5
- Transferring a negative amount to move money from the recipient to the sender
- Redeeming a referral bonus by referring yourself with a second account
- Re-using a single-use reset token or voucher that was never invalidated
- Purchasing an item that is out of stock due to a race condition between inventory check and reservation
- Accessing a premium subscription feature after downgrading to a free plan
- Winning an auction by retracting a high bid after others have been eliminated

The rest: https://github.com/utkusen/sast-skills/blob/HEAD/sast-files/.agents/skills/sast-businesslogic/SKILL.md