auditing-payment-state-machine-and-idempotency SKILL.md skillA
auditing-payment-state-machine-and-idempotency from unboundcompute/security-agent-skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add unboundcompute/security-agent-skills/auditing-payment-state-machine-and-idempotency@git:20260829.b60f9b2Pins git:20260829.b60f9b2 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- unboundcompute/security-agent-skills
- Path
skills/auditing-payment-state-machine-and-idempotency/SKILL.md- Versions recorded
- 1
- Latest version
- git:20260829.b60f9b2, committed Aug 29, 2026
- Size
- 10,077 bytes
- Repository stars
- 26
- License
- MIT
Audit payment and checkout state machines for transitions an attacker can drive out of order or replay for value: an order marked paid before the charge is confirmed, a step that can be skipped or repeated so goods ship without settlement, a non-idempotent charge or fulfillment endpoint that double-processes on a retried or replayed request, and a refund or cancel that returns value while the underlying charge stays captured. Covers checkout, charge, fulfillment, and refund flows where money…
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Auditing payment state machine and idempotency: value must not move faster than settlement A checkout is a state machine, and money moves through it in a strict order: an order is placed, a charge is authorized, the charge settles, and only then are goods fulfilled; refunds and cancels run the sequence backward. The bugs are transitions that break the order or repeat for value. An order marked paid before the charge is actually confirmed lets fulfillment run against a payment that never settles. A step that can be skipped, so fulfillment triggers without a completed charge, or repeated, so one payment yields multiple fulfillments, releases value the sequence did not authorize. A charge or fulfillment endpoint that is not idempotent double-processes when a request is retried or deliberately replayed, so a network retry or an attacker's repeat becomes two charges or two shipments. And a refund or cancel that returns value while the charge stays captured pays out twice. The audit walks the state machine and tries to move value ahead of, or more than once per, settlement. You audit this by driving transitions out of order and replaying the ones that release value. ## When to use …
Read the whole file at its exact version.
How to install
mdr add unboundcompute/security-agent-skills/auditing-payment-state-machine-and-idempotency@sha256:b4778d7cd9900780The line at the top of this page pins the label git:20260829.b60f9b2, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_gkbpbslv356gu4ax)
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Versions
The registry has recorded 1 version of this file, committed on Aug 29, 2026.
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (10077 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
unboundcompute/security-agent-skills · 26 stars · license MIT · pushed 2026-09-08 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_gkbpbslv356gu4ax GET https://markdownregistry.com/api/v1/resolve?ref=unboundcompute/security-agent-skills/auditing-payment-state-machine-and-idempotency GET https://markdownregistry.com/api/v1/blob/b4778d7cd99007807ad7019aad824d2e8e8504437d789351029bbdb7269bc924
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.