examples

Missing WITH CHECK Policy examples

These examples show how Missing WITH CHECK Policy problems ship in real apps — and what fixes actually work when tested via direct API access.

Why Missing WITH CHECK Policy examples matter

Attackers can impersonate other users or escalate privileges via unchecked writes. If Missing WITH CHECK Policy remains unresolved, attackers can automate enumeration and unauthorized writes at API speed. Treat it as a production reliability risk as well as a data security risk, because incidents spread quickly once clients discover weak access boundaries.

Examples about Missing WITH CHECK Policy

Example	Summary	URL
Missing WITH CHECK Policy: direct API bypass	Writes bypassed ownership checks because WITH CHECK was missing.	/examples/missing-with-check-policy/direct-api-bypass-missing-with-check-policy
Missing WITH CHECK Policy: migration drift regression	A migration introduced a table where writes lacked WITH CHECK, reopening a loophole.	/examples/missing-with-check-policy/migration-drift-missing-with-check-policy

Root cause → fix pattern analysis for Missing WITH CHECK Policy

Examples are most useful when you can translate them into a repeatable fix pattern. This table highlights the “why” behind each fix:

Example	Root cause	Fix pattern	URL
Missing WITH CHECK Policy: direct API bypass	Users could insert or update rows with other users’ IDs and escalate privileges.	Move writes behind backend endpoints that enforce ownership and mirror the read policy with WITH CHECK.	/examples/missing-with-check-policy/direct-api-bypass-missing-with-check-policy
Missing WITH CHECK Policy: migration drift regression	Without ownership checks on writes, attackers could insert or modify rows belonging to others.	Add WITH CHECK clauses, route writes through backend endpoints, and include policy verification steps in migrations.	/examples/missing-with-check-policy/migration-drift-missing-with-check-policy

How Missing WITH CHECK Policy failures typically happen

Adding only a SELECT policy and skipping WITH CHECK.
Assuming existing grants handle write restrictions.
Neglecting write exposure when auditing policies.

Fix patterns that tend to work for Missing WITH CHECK Policy

Across these examples, the highest-leverage fixes share a theme: remove direct client access and make verification repeatable.

Backend-only access for sensitive operations (server endpoints enforce authorization).
Least-privilege grants: revoke broad privileges from anon/authenticated.
Small, testable policies if you intentionally keep client access — avoid complex conditions.
A verification step that proves direct access fails (not just that the UI hides data).

How to spot Missing WITH CHECK Policy in your own project (signals)

A direct API call returns rows/files even when the UI is supposed to restrict them.
RLS/policies exist, but access still succeeds (often because RLS is disabled or policies are too broad).
Permissions depend on the client behaving “nicely” (UI checks) rather than the database enforcing access.
After a migration, access behavior changes unexpectedly (drift).

How to use these examples to fix your own app

Match the scenario to your table/bucket/function setup.
Identify the root cause (not just the symptom).
Apply the relevant template or conversion guide.
Verify direct access fails for client credentials.
Document the rule so it doesn’t regress.

Verification checklist for Missing WITH CHECK Policy fixes

Reproduce the issue once using direct API access (anon/authenticated) so you know it’s real.
Apply the fix pattern (backend-only access + least privilege) using a template.
Repeat the same direct access call and confirm it now fails.
Confirm the app still works via backend endpoints for authorized users.
Re-scan after the fix and add a drift guard for the next migration.

Preventing Missing WITH CHECK Policy regressions (drift guard)

Re-run the same direct access test after every migration that touches auth, policies, grants, Storage, or functions.
Keep a short inventory of sensitive resources and treat them as server-only by default.
Review new tables/buckets/functions in code review with an access-control checklist.
If you intentionally allow client access, document the policy rationale and add tests for it.

Optional SQL checks for Missing WITH CHECK Policy (extra confidence)

If you like having a repeatable “proof”, add a small set of SQL checks to your process.

Confirm RLS status for tables involved (enabled/forced where appropriate).
List policies and read them as plain language: who can do what under what condition?
Audit grants to anon/authenticated and PUBLIC for tables, views, and functions tied to this topic.
If Storage/RPC is involved, explicitly audit bucket settings and EXECUTE grants.

These checks complement (not replace) the direct access tests shown in the examples.

Decision guide for Missing WITH CHECK Policy: template vs conversion vs integration

If you’re here because you found this topic in a scan, the fastest path depends on whether the fix is a small config change or a workflow change.

Choose a template when you need a copy/paste change plus verification (tighten a policy/grant/bucket setting).
Choose a conversion when you need to change an access model end-to-end (unsafe → backend-only) with example transformations.
Choose an integration when the fix is a workflow pattern you’ll repeat (signed URLs, server-only RPC, backend endpoints).

If you’re unsure, start with the smallest template that removes direct client access, then add integrations for durability.

Evidence to keep after fixing Missing WITH CHECK Policy (makes reviews faster)

Teams often “fix” a topic but can’t prove it later. Save a few small artifacts so you can re-verify after migrations:

The direct access request you used before the fix (and the expected denial after).
A short boundary statement (who can access what, through which server endpoint).
The change you applied (policy/grant/bucket setting/EXECUTE revoke) and why.
The drift guard you’ll run after migrations (scan, checklist query, or release checklist item).

Glossary: Missing WITH CHECK Policy → /glossary/missing-with-check-policy
Template: Lock down a public table (backend-only access) → /templates/access-control/lock-down-public-table
Template: Remove over-permissive RLS policies (adopt deny-by-default) → /templates/access-control/remove-over-permissive-policies

What to do after you fix one example (so it stays fixed)

One fixed example is great — but the real win is preventing drift.

Write a one-sentence boundary statement (who can access what, through which server path).
Keep the one direct access test you used before the fix (and expect it to fail after).
Re-run the same test after migrations that touch policies, grants, buckets, or functions.

If you can re-run the test and it still fails, you’ve turned a one-time fix into a durable control.