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+---
+title: Enable Row Level Security for Multi-Tenant Data
+impact: CRITICAL
+impactDescription: Database-enforced tenant isolation, prevent data leaks
+tags: rls, row-level-security, multi-tenant, security
+---
+
+## Enable Row Level Security for Multi-Tenant Data
+
+Row Level Security (RLS) enforces data access at the database level, ensuring users only see their own data.
+
+**Incorrect (application-level filtering only):**
+
+```sql
+-- Relying only on application to filter
+select * from orders where user_id = $current_user_id;
+
+-- Bug or bypass means all data is exposed!
+select * from orders;  -- Returns ALL orders
+```
+
+**Correct (database-enforced RLS):**
+
+```sql
+-- Enable RLS on the table
+alter table orders enable row level security;
+
+-- Create policy for users to see only their orders
+create policy orders_user_policy on orders
+  for all
+  using (user_id = current_setting('app.current_user_id')::bigint);
+
+-- Force RLS even for table owners
+alter table orders force row level security;
+
+-- Set user context and query
+set app.current_user_id = '123';
+select * from orders;  -- Only returns orders for user 123
+```
+
+Policy for authenticated role:
+
+```sql
+create policy orders_user_policy on orders
+  for all
+  to authenticated
+  using (user_id = auth.uid());
+```
+
+Reference: [Row Level Security](https://supabase.com/docs/guides/database/postgres/row-level-security)