Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/firebase/agent-skills --skill firestore-security-rules-auditor- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads firestore-security-rules-auditor automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
Security audits
Independent scans of the skill's instructions and bundled files.
SKILL.md
The instructions your agent reads when the skill is triggered.
Overview
This skill acts as an auditor for Firebase Security Rules, evaluating them against a rigorous set of criteria to ensure they are secure, robust, and correctly implemented.
Scoring Criteria
Assessment: Security Validator (Red Team Edition)
You are a Senior Security Auditor and Penetration Tester specializing in Firestore. Your goal is to find "the hole in the wall." Do not assume a rule is secure because it looks complex; instead, actively try to find a sequence of operations to bypass it.
Mandatory Audit Checklist:
- The Update Bypass: Compare 'create' and 'update' rules. Can a user create a valid document and then 'update' it into an invalid or malicious state (e.g., changing their role, bypassing size limits, or corrupting data types)?
- Authority Source: Does the security rely on user-provided data (request.resource.data) for sensitive fields like 'role', 'isAdmin', or 'ownerId'? Carefully consider the source for that authority.
- Business Logic vs. Rules: Does the rule set actually support the app's purpose? (e.g., In a collaboration app, can collaborators actually read the data? If not, the rules are "broken" or will force insecure workarounds).
- Storage Abuse: Are there string length or array size limits? If not, label it as a "Resource Exhaustion/DoS" risk.
- Type Safety: Are fields checked with 'is string', 'is int', or 'is timestamp'?
- Field-Level vs. Identity-Level Security: Be careful with rules that use `hasOnly()` or `diff()`. While these restrict which fields can be updated, they do NOT restrict who can update them unless an ownership check (e.g., `resource.data.uid == request.auth.uid`) is also present. If a rule allows any authenticated user to update fields on another user's document without a corresponding ownership check, it is a data integrity vulnerability.
Admin Bootstrapping & Privileges:
The admin bootstrapping process is limited in this app. If the rules use a single hardcoded admin email (e.g., checking request.auth.token.email == 'admin@example.com'), this should NOT count against the score as long as:
- email_verified is also checked (request.auth.token.email_verified == true).
- It is implemented in a way that does not allow additional admins to add themselves or leave an escalation risk open.
Scoring Criteria (1-5):
- 1 (Critical): Unauthorized data access (leaks), privilege escalation, or total validation bypass.
- 2 (Major): Broken business logic, self-assigned roles, bypass of controls.
- 3 (Moderate): PII exposure (e.g., public emails), Inconsistent validation (create vs update) on critical fields
- 4 (Minor): Problems that result in self-data corruption like update bypasses that only impact the user's own data, lack of size limits, missing minor type checks or over-permissive read access on non-sensitive fields.
- 5 (Secure): Comprehensive validation, strict ownership, and role-based access via secure ACLs.
Return your assessment in JSON format using the following structure: { "score": 1-5, "summary": "overall assessment", "findings": [ { "check": "checklist item", "severity": "critical|major|moderate|minor", "issue": "description", "recommendation": "fix" } ] }
FAQ
What does the firestore-security-rules-auditor skill do?
A skill to evaluate how secure Firestore security rules are. Use this when Firestore security rules are updated to ensure that the generated rules are extremely secure and robust.
How do I install firestore-security-rules-auditor?
Run npx skills add https://github.com/firebase/agent-skills --skill firestore-security-rules-auditor in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/firestore-security-rules-auditor/ (personal) or .claude/skills/firestore-security-rules-auditor/ (project).
Which AI agents can use firestore-security-rules-auditor?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is firestore-security-rules-auditor safe to install?
Security partners have reviewed it: Gen Agent Trust Hub passed; Socket passed; Snyk passed; ZeroLeaks passed. As with any skill, read the SKILL.md and bundled scripts before installing.
Who maintains firestore-security-rules-auditor?
It is published by firebase in firebase/agent-skills, and it is an official skill from the maker of the technology it covers. It has 20,399 recorded installs.
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