business-logic-flaws

business-logic-flaws is a skill for Claude Code, Codex from ShulkwiSEC/bb-huge. It costs 98 tokens per session (1,869 once invoked), scanned A, original, MIT.

A guide to business logic flaws, where an application follows its technical rules but allows an unintended result. Examples include changing prices, reusing coupons, skipping workflow steps, or exploiting timing gaps.

In plain words
What is it for?
Use it to test checkout, discounts, payments, account permissions, and multi-step processes for price manipulation, limit bypasses, race conditions, or privilege changes.
Why use it?
These problems depend on how a product is meant to work, so standard vulnerability scanners often miss them. The guide helps testers examine assumptions in real user workflows.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions Claude Code.

Good fit Use it to test checkout, discounts, payments, account permissions, and multi-step processes for price manipulation, limit bypasses, race conditions, or privilege changes.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/shulkwisec/bb-huge/business-logic-flaws
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 ShulkwiSEC/bb-huge --skill business-logic-flaws
Clone the repo
git clone --depth 1 https://github.com/ShulkwiSEC/bb-huge

Made for: Claude Code, Codex.

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-flaws

README.md
[![agentmods](https://agentmods.dev/badge/skills/shulkwisec/bb-huge/business-logic-flaws/github.svg)](https://agentmods.dev/skills/shulkwisec/bb-huge/business-logic-flaws)
Your own site
<a href="https://agentmods.dev/skills/shulkwisec/bb-huge/business-logic-flaws"><img src="https://agentmods.dev/badge/skills/shulkwisec/bb-huge/business-logic-flaws/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-flaws

Your own site · 80×15
<a href="https://agentmods.dev/skills/shulkwisec/bb-huge/business-logic-flaws"><img src="https://agentmods.dev/badge/skills/shulkwisec/bb-huge/business-logic-flaws.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 98 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,869 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. 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 $0.00098 $0.01869
Opus 5 $0.00049 $0.00934
Sonnet 5 $0.00020 $0.00374
Haiku 4.5 $0.00010 $0.00187

Measured 7d ago against content hash 7dc77441a3b4, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

business-logic-flaws scanned grade A with 1 finding 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 7d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -s -b "session=TOKEN" TARGET/orders/1001
skills/curated/business-logic-flaws/SKILL.md · 157 lines

How it starts

The opening of the file, as written. The whole thing — 157 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Business Logic Flaws

What Is Broken and Why

Business logic flaws occur when an application's security controls are implemented only on the client side, or when developers assume users will always follow the intended workflow. Unlike injection attacks, these vulnerabilities use the application's own features correctly from a technical standpoint but in unintended sequences or with unexpected values. They are particularly dangerous because automated scanners rarely detect them — they require understanding the application's intended purpose. Common manifestations include price/quantity manipulation, workflow step bypass, coupon reuse, race conditions in financial operations, and privilege escalation via hidden or predictable parameters.

Key Signals

  • Hidden form fields containing prices, discount amounts, user roles, or IDs
  • Multi-step purchase/checkout workflows where steps can be skipped via direct URL navigation
  • Coupon or discount codes accepted multiple times
  • Pricing or quantity fields not validated server-side (only validated in JavaScript)
  • Parameters incrementing predictably (orderId=1001, 1002…) suggesting enumerable resources
  • Time-sensitive operations (balance checks, reservation holds) that can be exploited between check and action
  • Admin or privilege flags passed in HTTP parameters
  • Audit log endpoints with insufficient access controls

Methodology

  1. Data Validation Testing (BUSL-01)

    • Identify all data entry and handoff points between system components
    • Intercept HTTP requests and submit logically invalid values: negative quantities, non-existent IDs, out-of-range prices
    • Verify server rejects logically invalid data (not just client-side validation)
  2. Request Forging (BUSL-02)

    • Monitor POST/GET for guessable or predictable parameter values
    • Identify hidden features (debug flags, admin toggles) in HTTP parameters
    • Modify discovered values to test for unintended access or behavior
  3. Integrity Check Testing (BUSL-03)

    • Compare hidden HTTP fields against visible GUI fields
    • Submit alternative values in "read-only" fields via proxy
    • Test log file and audit trail manipulation via unauthorized access

Read the full file on GitHub · 157 lines

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. 7d ago First seen · 157 lines · 98 tokens per session scan A 7dc77441a3b4

Subscribe to this mod's changes

business-logic-flaws is a skill published in the GitHub repository ShulkwiSEC/bb-huge (22 stars, last pushed 2mo ago), licensed MIT. It adds 98 tokens to every session and 1,869 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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