Business Logic Analysis

Business Logic Analysis is a skill for Claude Code from allsmog/vuln-scout. It costs 61 tokens per session (2,037 once invoked), scanned A, original, MIT.

A guide to finding security flaws in an application's intended workflows, such as checkout, registration, or account access. These flaws happen when users can perform valid actions in an unintended order or combination.

In plain words
What is it for?
Use it to review roles, permissions, trust boundaries, and multi-step processes for authorization bypasses and workflow vulnerabilities.
Why use it?
Traditional checks may miss abuse of normal features, such as skipping a required step or accessing another user's operation. This guide helps reviewers understand the application before testing its rules.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the vuln-scout plugin — 32 skills, 15 commands, 9 agents shipped together

Good fit Use it to review roles, permissions, trust boundaries, and multi-step processes for authorization bypasses and workflow vulnerabilities.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/allsmog/vuln-scout/business-logic
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add allsmog/vuln-scout --skill business-logic
Clone the repo
git clone --depth 1 https://github.com/allsmog/vuln-scout

Made for: Claude Code.

Or install vuln-scout, the plugin that ships this one along with the rest of its 32 skills, 15 commands, 9 agents.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for Business Logic Analysis

README.md
[![agentmods](https://agentmods.dev/badge/skills/allsmog/vuln-scout/business-logic/github.svg)](https://agentmods.dev/skills/allsmog/vuln-scout/business-logic)
Your own site
<a href="https://agentmods.dev/skills/allsmog/vuln-scout/business-logic"><img src="https://agentmods.dev/badge/skills/allsmog/vuln-scout/business-logic/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for Business Logic Analysis

Your own site · 80×15
<a href="https://agentmods.dev/skills/allsmog/vuln-scout/business-logic"><img src="https://agentmods.dev/badge/skills/allsmog/vuln-scout/business-logic.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,037 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00061 $0.02037
Opus 5 $0.00030 $0.01019
Sonnet 5 $0.00012 $0.00407
Haiku 4.5 $0.00006 $0.00204

Measured 12d ago against content hash 9e041b97419c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

Business Logic Analysis scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

vuln-scout/skills/business-logic/SKILL.md · 261 lines

How it starts

The opening of the file, as written. The whole thing — 261 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Business Logic Analysis

Purpose

Provide comprehensive knowledge of business logic vulnerabilities - flaws that arise from incorrect assumptions about how users will interact with an application, rather than from traditional injection or parsing errors.

Key Insight: Unlike technical vulnerabilities (SQLi, XSS), business logic flaws require deep understanding of what the application is supposed to do. You cannot find them without first understanding the application.


When to Use

Activate this skill when:

  • Beginning a whitebox security review (understand before hunt)
  • Analyzing multi-step workflows (checkout, registration, auth)
  • Reviewing authorization and access control
  • Looking for ways to abuse intended functionality
  • Identifying trust boundaries between components

Core Concepts

1. Deep Application Understanding

Before hunting for business logic bugs:

  1. Understand the application's purpose
  2. Map all user roles and permissions
  3. Identify critical workflows (money, data, access)
  4. Document trust assumptions between components
  5. Model state machines for multi-step processes

2. Trust Boundaries

Trust boundaries exist where:

  • Frontend communicates with backend
  • Service A calls Service B
  • Application trusts database content
  • External APIs are consumed
  • User-controlled data crosses privilege levels

Common flaw: Backend trusts frontend validation, allowing bypass.

3. State Machine Vulnerabilities

Multi-step processes have states. Vulnerabilities arise from:

  • Skipping states (jump from step 1 to step 4)
  • Invalid transitions (completed → pending)
  • Replaying states (submit same step twice)
  • Concurrent state manipulation (race)

Vulnerability Categories

Authorization Logic Flaws

Flaw Pattern Impact
IDOR Direct object reference without ownership check Access other users' data
Horizontal Privilege Escalation Role check missing on specific action Act as peer user
Vertical Privilege Escalation Admin function callable by regular user Gain admin access
Function-Level Access Control Endpoint has no auth check Bypass authentication

Read the full file on GitHub · 261 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 12d ago First seen · 261 lines · 61 tokens per session scan A 9e041b97419c

Subscribe to this mod's changes

Business Logic Analysis is a skill published in the GitHub repository allsmog/vuln-scout (24 stars, last pushed 3mo ago), licensed MIT. It adds 61 tokens to every session and 2,037 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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