Prevent Devastating Data Leaks: Securing Supabase RLS Against AI Vulnerabilities

The Critical Risk: Why AI Coding Assistants Skip Row-Level Security#

Row-Level Security (RLS) is your ultimate defense layer against catastrophic data breaches when building with Supabase. By default, PostgreSQL tables in Supabase may expose confidential user profiles, payment tokens, and corporate IP to unauthorized public endpoints if RLS is omitted.

3-Step Zero-Leak Database Hardening Checklist#

Execute these mandatory security steps across all your production Supabase database instances:

-- Step 1: Enable RLS on every public table
ALTER TABLE public.profiles ENABLE ROW LEVEL SECURITY;
ALTER TABLE public.domains ENABLE ROW LEVEL SECURITY;
ALTER TABLE public.domain_tasks ENABLE ROW LEVEL SECURITY;

-- Step 2: Enforce strict user-bound access policy
CREATE POLICY "Users can only view their own profile"
  ON public.profiles
  FOR SELECT
  USING (auth.uid() = id);

-- Step 3: Enforce strict user-bound mutation policy
CREATE POLICY "Users can only update their own profile"
  ON public.profiles
  FOR UPDATE
  USING (auth.uid() = id)
  WITH CHECK (auth.uid() = id);

Advanced Privilege Escalation Protection#

When writing PostgreSQL trigger functions or background jobs:

1. 1
   **Use SECURITY INVOKER by Default**: Functions execute with the privileges of the calling user, respecting all RLS table policies.
2. 2
   **Use SECURITY DEFINER with Explicit Search Path**: When elevated privileges are mandatory (e.g. creating profile records on user signup), always set SET search_path = public to prevent search-path injection vulnerabilities.
3. 3
   Avoid Recursive RLS Queries: Never query the profiles table inside an RLS check on profiles. Instead, create a dedicated is_admin() PostgreSQL helper function marked SECURITY DEFINER.