Supabase Security Templates

What these Supabase security templates are for

These pages exist for one reason: make secure changes easy to apply and easy to verify.

Each template includes:

• Copy/paste or step-by-step instructions (no hand-wavy guidance)
• Multiple variations so you can choose the safest option that fits your situation
• Verification steps (so you know the fix actually worked)

Supabase templates by category

How to choose the right template

1. Start with exposure: public tables, public/listable storage, and public RPC are the highest leverage fixes.
2. Prefer backend-only access patterns first; they reduce entire classes of policy mistakes.
3. Apply changes with a verification checklist (direct client access should fail).
4. After fixing, re-scan to ensure regressions don’t ship later.

Popular templates

• Lock down a public table (backend-only access) → /templates/access-control/lock-down-public-table — A template to revoke direct client access, enable RLS, remove policies, and force all reads/writes through your backend using service_role.
• Lock down RPC: revoke EXECUTE from public roles → /templates/rpc-functions/lock-down-rpc-execute — A template to discover function signatures, revoke EXECUTE from PUBLIC/anon/authenticated, and call RPC only through backend code using service_role.
• Make a bucket private + serve files with signed URLs → /templates/storage-safety/make-bucket-private-signed-urls — A template to make Supabase Storage buckets private, prevent listing/enumeration, and deliver downloads using short-lived signed URLs from your backend.
• Remove over-permissive RLS policies (adopt deny-by-default) → /templates/access-control/remove-over-permissive-policies — A template to remove broad policies that leak data and move to a backend-only, deny-by-default posture that is easier to reason about and verify.

How templates connect to conversions and examples

Templates are meant to be applied, not admired. They work best when you pair them with two other playbooks:

• Conversions explain the whole transformation (from unsafe → safe) so you don’t miss steps like updating frontend call paths.
• Examples show how the exposure shipped and why a fix pattern works, which helps you generalize safely.

A good workflow is: scan → pick a template → apply + verify → follow cross-links to the conversion/example pages for deeper context.

Verification mindset (avoid false confidence)

• Don’t trust the UI. Validate by attempting direct API access with client credentials.
• Don’t fix one surface and ignore others. Storage and RPC commonly remain exposed.
• Don’t ship unverified policies. If you can’t explain the policy condition clearly, it’s probably too broad.
• Don’t rely on obscurity (IDs and filenames are often enumerable).

Rollback and safety notes (ship fixes confidently)

• Apply changes in staging first when possible, then repeat the same verification checklist in production.
• Prefer additive migrations and feature flags for backend endpoints before revoking client access (reduces downtime risk).
• If a fix breaks something, roll back the application path first — but keep the direct-access exposure blocked unless you intentionally accept the risk.
• Document the “why” and the verification steps so future schema changes don’t reintroduce the issue.

If you can’t find a template that matches your issue

Don’t force-fit the closest template if it’s the wrong surface. Instead:

• Start in /glossary to name the exact failure mode (public read, public write, enumeration, leaked secret).
• Jump to /examples to find a scenario that matches how your exposure shipped.
• Use /conversions when the fix is architectural (unsafe → backend-only).
• If you’re still unsure, run a scan and follow the linked fix pattern for the finding.

The goal is not “apply any template” — it’s “apply the right fix and prove direct access is blocked.”