stripe-security

stripe-security is a skill for Claude Code from coldtatooine/vuln-skill-pack. It costs 48 tokens per session (950 once invoked), scanned A, original, MIT.

A set of checks for reviewing Stripe payment and subscription code, including webhooks and fulfillment.

In plain words
What is it for?
Use it when building or reviewing Stripe Checkout, Payment Intents, subscriptions, webhooks, and payment-related fulfillment.
Why use it?
It helps find mistakes that could allow fake payments, expose secret keys, charge incorrectly, or repeat side effects.

Skill for Claude Code

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

Part of the vun-skill-pack plugin — 5 skills, 11 commands, 1 agent, 1 hook shipped together

Good fit Use it when building or reviewing Stripe Checkout, Payment Intents, subscriptions, webhooks, and payment-related fulfillment.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/coldtatooine/vuln-skill-pack/stripe-security
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 coldtatooine/vuln-skill-pack --skill stripe-security
Clone the repo
git clone --depth 1 https://github.com/coldtatooine/vuln-skill-pack

Made for: Claude Code.

Or install vun-skill-pack, the plugin that ships this one along with the rest of its 5 skills, 11 commands, 1 agent, 1 hook.

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 stripe-security

README.md
[![agentmods](https://agentmods.dev/badge/skills/coldtatooine/vuln-skill-pack/stripe-security/github.svg)](https://agentmods.dev/skills/coldtatooine/vuln-skill-pack/stripe-security)
Your own site
<a href="https://agentmods.dev/skills/coldtatooine/vuln-skill-pack/stripe-security"><img src="https://agentmods.dev/badge/skills/coldtatooine/vuln-skill-pack/stripe-security/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 stripe-security

Your own site · 80×15
<a href="https://agentmods.dev/skills/coldtatooine/vuln-skill-pack/stripe-security"><img src="https://agentmods.dev/badge/skills/coldtatooine/vuln-skill-pack/stripe-security.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 48 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 950 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 $0.00048 $0.00950
Opus 5 $0.00024 $0.00475
Sonnet 5 $0.00010 $0.00190
Haiku 4.5 $0.00005 $0.00095

Measured 10d ago against content hash b586c8f91d1c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

stripe-security 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 10d 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.

skills/stripe-security/SKILL.md · 61 lines

How it starts

The opening of the file, as written. The whole thing — 61 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Stripe Security Footguns

Apply when the app integrates Stripe (Checkout, Payment Intents, Subscriptions, webhooks). Payment code moves money, so bugs are directly monetizable. Pair with /scan, /preflight, /secrets.

Verify before flagging

  • pk_* in the client / public env is expected; only flag sk_*, rk_*, whsec_* outside server-only contexts.
  • Distinguish test vs live keys: still flag committed secret keys, but treat live as higher severity.
  • Missing idempotency is a finding when fulfillment has side effects (credits, shipping, entitlements) — not every read-only webhook handler.
  • livemode checks matter when production must ignore test events (or vice versa); don't flag if both modes are intentionally handled.

1. Webhook signature verification (Critical)

  • Every webhook endpoint must verify the Stripe signature using the endpoint's signing secret (stripe.webhooks.constructEvent(rawBody, sig, secret)). Without it, anyone can POST a fake checkout.session.completed and get free fulfillment.
  • Use the raw request body, not parsed JSON. Frameworks that auto-parse the body (Express json(), Next.js default body parsing) break verification — the signature is computed over raw bytes. Disable body parsing on the webhook route.
  • Reject on verification failure. Don't fall through to processing.
  • Allowlist event types you handle; ignore or reject unexpected types instead of a catch-all switch that fulfills on anything.
  • If production should only process live traffic, check event.livemode (or equivalent) before fulfilling.

2. Never trust amounts or entitlements from the client

  • Price/amount must come from the server, looked up from your product catalog by product ID — never sent from the browser. A client that posts amount: 1 to your Payment Intent creation pays 1 cent for a $100 item.
  • Same for quantity, currency, discount, and entitlement (which plan/features the user gets). Compute server-side from trusted data.
  • With Checkout, prefer server-created line_items referencing Stripe Price IDs over client-supplied price_data.

Read the full file on GitHub · 61 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. 10d ago First seen · 61 lines · 0 tokens per session scan A b586c8f91d1c

Subscribe to this mod's changes

stripe-security is a skill published in the GitHub repository coldtatooine/vuln-skill-pack (2 stars, last pushed 15d ago), licensed MIT. It adds 48 tokens to every session and 950 once invoked, about $0.0002 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 2026-08-31.

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