Firebase Security Rules Auditor

Firebase (Google)OfficialCreated by Google LLCDistributed by Firebase (Google)

Skill
Review and audit
Security
Apache-2.0
No issues found

From the author

Audits Firebase (Firestore, Cloud Storage) security rules for vulnerabilities, privilege escalation, role bypasses, create vs update inconsistencies, resource exhaustion, type safety, size limits, and hasOnly ownership checks. Use when auditing/reviewing rules, running red-team rule assessments, or scoring against auditor checklists. Don't use for Firebase CLI (login, deploy), Auth, Crashlytics, Remote Config, or database queries.

— the description by Google LLC

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

The Firebase Security Rules Auditor acts as a senior security consultant, systematically evaluating Firestore and Cloud Storage rulesets. It employs a red-team methodology to stress-test access controls, data validation, and ownership logic. By checking against a structured checklist—including update bypasses, resource exhaustion risks, and type safety—it provides a quantitative security score and actionable remediation steps for developers.

What it does

Evaluates Firestore and Cloud Storage rules for privilege escalation and unauthorized access.
Identifies inconsistencies between create and update operations that could lead to data corruption.
Detects potential resource exhaustion vulnerabilities such as missing size or length limits.
Verifies the integrity of ownership checks and field-level security implementations.
Provides a structured security score from 1 (Critical) to 5 (Secure) for the ruleset.
Generates a detailed JSON report containing specific findings and recommended fixes.

When to use it

During the code review process for new Firebase security rules.
When conducting a red-team assessment of existing database access controls.
To validate that business logic requirements are correctly enforced by security rules.
When auditing rules for potential data integrity or privilege escalation vulnerabilities.

Advantages

Standardizes the security review process for Firebase projects.
Focuses on common, high-impact vulnerabilities like update bypasses and role escalation.
Provides clear, actionable recommendations for hardening security configurations.
Uses a consistent scoring system to track security posture over time.

Usage examples

“Audit my Firestore security rules for potential privilege escalation and update bypasses.”: The agent analyzes the rules, identifies if users can modify sensitive fields like 'role' during updates, and returns a JSON report with a severity score and remediation steps.
“Review my Cloud Storage rules for resource exhaustion risks.”: The agent checks for missing string length or array size limits and reports any findings that could lead to potential DoS vulnerabilities.

Install

Download the skill as a ZIP:
https://autogineer.com/agent-skills/firebase/firebase-security-rules-auditor/download

Unzip it into the cross-client skills folder of your project:

mkdir -p .agents/skills && unzip firebase-security-rules-auditor.zip -d .agents/skills

Documentation by Google LLC

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 == '[email protected]'), 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,
  "summary": "overall assessment",
  "findings": [
    {
      "check": "checklist item",
      "severity": "critical|major|moderate|minor",
      "issue": "description",
      "recommendation": "fix"
    }
  ]
}

Files

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Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Security

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Attribution and licence

Created by

Google LLC

Publisher

Firebase (Google) (Official)

Distributed by

Firebase (Google)

Source

firebase/agent-skills · skills/firebase-security-rules-auditor · commit b76be96

Licence

Apache License 2.0 (redistribution allowed)

LICENSE (added by AutoGineer from LICENSE)
ATTRIBUTION.md (written by AutoGineer)

Synced

2026-11-09

AutoGineer is not affiliated with or endorsed by Google LLC or Firebase (Google).

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