rc-security

rc-security is a skill for Claude Code from RevenueCat/ai-toolkit. It costs 64 tokens per session (1,528 once invoked), scanned A, original, MIT.

A security review guide for RevenueCat purchases on Android. It covers how purchase information is checked, how users are identified, and how public and secret API keys should be used.

In plain words
What is it for?
Use it to review entitlement verification, API-key placement, anonymous and logged-in users, purchase-token handling, and server-side access checks.
Why use it?
It helps prevent unauthorised access caused by trusting unchecked responses, exposing a secret key, using unclear user identities, or accepting unsafe purchase data. It also explains which protections RevenueCat already provides and which access decisions belong on your server.

Skill for Claude Code

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

Part of the revenuecat-play-billing plugin — 20 skills shipped together

Good fit Use it to review entitlement verification, API-key placement, anonymous and logged-in users…

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/revenuecat/ai-toolkit/rc-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 RevenueCat/ai-toolkit --skill rc-security
Clone the repo
git clone --depth 1 https://github.com/RevenueCat/ai-toolkit

Made for: Claude Code.

Or install revenuecat-play-billing, the plugin that ships this one along with the rest of its 20 skills.

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 rc-security

README.md
[![agentmods](https://agentmods.dev/badge/skills/revenuecat/ai-toolkit/rc-security.svg)](https://agentmods.dev/skills/revenuecat/ai-toolkit/rc-security)
Your own site
<a href="https://agentmods.dev/skills/revenuecat/ai-toolkit/rc-security"><img src="https://agentmods.dev/badge/skills/revenuecat/ai-toolkit/rc-security.svg" alt="Measured on agentmods" height="20"></a>
Per session 64 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,528 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 $0.00064 $0.01528
Opus 5 $0.00032 $0.00764
Sonnet 5 $0.00013 $0.00306
Haiku 4.5 $0.00006 $0.00153

Measured 7d ago against content hash cb70570da05e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

rc-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 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.

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.

revenuecat-play-billing/skills/rc-security/SKILL.md · 158 lines

How it starts

The opening of the file, as written. The whole thing — 158 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Phase 0: Intent

Tell the user: "I will review your RevenueCat security posture on Android: verification mode, API keys, user identity, and server side access decisions."

Phase 1: Discovery

Confirm what RevenueCat already covers so you can focus on the real gaps.

Concern Who handles it How
Receipt validation against Google Play RevenueCat backend Runs before awaitPurchase() returns
Purchase token reuse RevenueCat backend Tokens are deduplicated server side
Fabricated purchase tokens RevenueCat backend Fails Google Play verification, no entitlement granted
HTTPS transport to RevenueCat SDK Always on
Retry of token post on network failure SDK Retries on next app launch

Ask the project these questions:

  • Is EntitlementVerificationMode set? If not, CustomerInfo responses are trusted without signature checking.
  • Is the SDK configured with the public Android key (starts with goog_) or has someone accidentally pasted the secret key into the client?
  • Are real users identified with Purchases.logIn(yourUserId), or is the app still relying on anonymous $RCAnonymousID:...?
  • Do server endpoints that serve premium content verify entitlement server side, or do they trust a client sent flag?

Phase 2: Plan

Decide each of the following before changing code.

Decision A: Entitlement verification mode

Mode Failed verification does what Pick when
DISABLED (default) No signing happens Only for quick prototypes
INFORMATIONAL Logged, access still granted You want signal without risking false denials to real users
ENFORCED EntitlementInfo.isActive returns false You accept some false negatives from proxies or VPNs in exchange for a strict client guarantee

Decision B: Where is the authority?

Even with ENFORCED, the client is not the authority for paid content. Decide whether each premium endpoint:

  1. Calls the RevenueCat REST API per request, or
  2. Reads a local has_entitlement flag driven by RevenueCat webhooks.

Read the full file on GitHub · 158 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 · 158 lines · 64 tokens per session scan A cb70570da05e

Subscribe to this mod's changes

rc-security is a skill published in the GitHub repository RevenueCat/ai-toolkit (65 stars, last pushed 5d ago), licensed MIT. It adds 64 tokens to every session and 1,528 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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