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.
npx agentmods add rules/coldtatooine/vuln-skill-pack/stripe-securitygit clone --depth 1 https://github.com/coldtatooine/vuln-skill-packWrote 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.
[](https://agentmods.dev/rules/coldtatooine/vuln-skill-pack/stripe-security)<a href="https://agentmods.dev/rules/coldtatooine/vuln-skill-pack/stripe-security"><img src="https://agentmods.dev/badge/rules/coldtatooine/vuln-skill-pack/stripe-security.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00000 | $0.00552 |
| Opus 5 | $0.00000 | $0.00276 |
| Sonnet 5 | $0.00000 | $0.00110 |
| Haiku 4.5 | $0.00000 | $0.00055 |
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 5d 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.
How it starts
The opening of the file, as written. The whole thing — 34 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Stripe Security Footguns
Payment code moves money, so bugs are directly monetizable.
1. Webhook signature verification (Critical)
- Every webhook endpoint must verify the Stripe signature with the endpoint signing secret (
stripe.webhooks.constructEvent(rawBody, sig, secret)). Without it, anyone can POST a fakecheckout.session.completedand get free fulfillment. - Use the raw request body, not parsed JSON — the signature is computed over raw bytes. Frameworks that auto-parse (Express
json(), Next.js default parsing) break verification; disable body parsing on the webhook route. - Reject on verification failure; don't fall through to processing.
2. Never trust amounts or entitlements from the client
- Price/amount comes from the server, looked up by product ID — never sent from the browser. A client posting
amount: 1pays 1 cent for a $100 item. - Same for quantity, currency, discount, entitlement. With Checkout, prefer server-created
line_itemsreferencing Stripe Price IDs over client-suppliedprice_data.
3. Fulfill on the right event
- Grant access / ship on the verified webhook (
checkout.session.completed,payment_intent.succeeded,invoice.paid) — not on the browser redirect to the success URL (reachable without paying). Checkpayment_status === 'paid'before fulfilling.
4. Secret key exposure
sk_live_*/sk_test_*/rk_*andwhsec_*are server-only. Onlypk_*publishable keys belong in the browser. Leaked secret key → rotate immediately (Critical).
5. Idempotency & abuse
- Webhooks can be delivered more than once — make fulfillment idempotent (track processed
event.id) so retries don't double-grant or double-ship. - Rate-limit payment-creation endpoints to prevent card-testing abuse.
6. Other
- Don't log full Stripe objects (PII / partial card data) — redact.
- Verify the authenticated user owns the session/subscription they act on (IDOR into another's billing).
- Handle disputed/refunded/
subscription.deletedevents to revoke access.
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.
- 5d ago First seen · 34 lines · 0 tokens per session scan A ad78f54fb21b
stripe-security is a cursor rule published in the GitHub repository coldtatooine/vuln-skill-pack (2 stars, last pushed 11d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 552 tokens. 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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