How I Would Fix exposed API keys and missing auth in a Supabase and Edge Functions marketplace MVP Using Launch Ready.

How I Would Fix exposed API keys and missing auth in a Supabase and Edge Functions marketplace MVP Using Launch Ready

The symptom is usually blunt: a marketplace MVP works in the browser, but anyone can hit the API, scrape data, create listings, or trigger Edge Functions with a copied key. In Supabase projects, this often comes from shipping with the anon key exposed in client code, using service role secrets in the wrong place, or skipping Row Level Security entirely.

The first thing I would inspect is whether the app is relying on client-side trust for anything sensitive. I would check Supabase auth settings, RLS status on every table, Edge Function headers, environment variables in the deployment platform, and whether any private keys were committed to Git history or baked into frontend bundles.

Triage in the First Hour

1. Check the live app bundle for secrets.

• Open DevTools and search the loaded JS for `service_role`, `supabase.co`, or hardcoded tokens.
• If a secret is visible in browser code, treat it as compromised.

2. Inspect Supabase dashboard settings.

• Confirm which keys are public anon keys and which are service role keys.
• Review Auth providers, JWT settings, and active users.

3. Audit table security in Supabase.

• Check every marketplace table for RLS enabled or disabled.
• Look at policies on listings, orders, messages, payments, profiles, and admin tables.

4. Review Edge Functions logs.

• Look for requests without valid JWTs.
• Check whether functions accept requests from any origin or anonymous caller.

5. Review deployment environment variables.

• Confirm secrets are only stored server-side.
• Check Vercel, Netlify, Cloudflare Pages, or similar for leaked variables.

6. Scan recent Git commits and build artifacts.

• Search commit history for `.env`, API keys, service role strings, or pasted JSON credentials.
• Check if preview builds exposed admin endpoints.

7. Confirm account-level exposure.

• Rotate any key that may have been exposed.
• Review logs for suspicious spikes in reads, writes, or function invocations.

8. Freeze risky writes if needed.

• If unauthorized creation or edits are possible, temporarily disable write paths while fixing auth.

A simple diagnostic command I would run early:

grep -R "service_role\|SUPABASE_ANON_KEY\|SUPABASE_SERVICE_ROLE_KEY" . \
  --exclude-dir=node_modules --exclude-dir=.next --exclude-dir=dist

If that finds anything inside frontend code or checked-in files, I already know this is not just an auth bug. It is a production safety issue with possible data exposure.

Root Causes

1. Service role key used in client-side code

• Confirmation: search the frontend bundle and source files for `service_role`.
• Why it matters: this key bypasses RLS and can read or write everything in the database.

2. RLS disabled on core tables

• Confirmation: inspect each table in Supabase and see if RLS is off.
• Why it matters: even with a public anon key, disabled RLS can allow unauthorized access to marketplace data.

3. Missing or weak policies

• Confirmation: RLS is on, but policies are too broad such as `using (true)` or `with check (true)`.
• Why it matters: users can see other sellers' listings or modify records they do not own.

4. Edge Functions accept unauthenticated requests

• Confirmation: function logs show requests without verified JWTs or user context.
• Why it matters: anyone can trigger privileged actions like payout setup, listing moderation, or internal sync jobs.

5. Secrets stored in the wrong place

• Confirmation: secrets exist in frontend env files like `.env.local` but are referenced by client components.
• Why it matters: build tooling can expose them during compilation or runtime inspection.

6. No rate limiting or abuse controls

• Confirmation: repeated requests from one IP create large log spikes or duplicate records.
• Why it matters: even after auth is added, abuse can still burn compute and create support noise.

The Fix Plan

I would fix this in a controlled order so I do not break production while closing the hole.

1. Rotate exposed credentials first

• Regenerate any leaked Supabase keys immediately.
• Replace them everywhere they are used server-side.
• Assume anything visible in browser code has already been copied.

2. Separate public and private access cleanly

• Keep only the anon key in frontend code if needed for public reads through RLS-protected tables.
• Move service role usage into server-only routes or Edge Functions that verify identity before doing anything privileged.

3. Turn on RLS everywhere sensitive data exists

• Enable RLS on all marketplace tables that store users, listings, orders, messages, reviews, payouts, admin notes, and internal metadata.
• Do not leave one table open because "it is just temporary." Temporary becomes permanent fast.

4. Write narrow policies by ownership and role

• Buyers should only read what they need to see.
• Sellers should only manage their own listings and orders tied to them.
• Admin actions should require explicit admin claims or a separate admin table checked server-side.

5. Lock down Edge Functions

• Require a valid Supabase JWT for protected functions.
• Verify user identity inside each function before using elevated privileges.
• Reject missing auth early with clear 401 responses.

6. Move secret-dependent logic server-side

• Anything involving Stripe webhooks validation, payout provider calls, moderation tools, admin syncs, email sending tokens, or database writes with elevated access should run only on trusted server paths.

7. Add CORS and origin checks where appropriate

• Allow only your production domain and known preview domains if needed.
• Do not rely on CORS as security by itself. It is only one layer.

8. Add logging without leaking secrets

• Log request IDs, user IDs where safe, action names, status codes, and error classes.
• Never log access tokens, raw Authorization headers, service role values, or personal data dumps.

9. Put a temporary guardrail on writes if exposure was broad

• If you suspect mass unauthorized access was possible yesterday morning until now,

I would pause sensitive mutations until policies are verified and logs reviewed.

10. Deploy behind a small verification window

• Ship to staging first if available.
• Then deploy production during a low-traffic window with monitoring open for 30 to 60 minutes after release.

Here is the decision path I would follow:

My recommendation is one path only: fix auth at the database layer first with RLS plus narrow policies, then harden Edge Functions second. If you start with UI guards alone, you will still have an exposed backend that anyone can call directly.

Regression Tests Before Redeploy

I would not redeploy until these pass:

1. Anonymous user cannot read private data

• Try listing endpoints without login.
• Expected result: public data only where intended; private records return empty sets or 401/403.

2. User cannot access another user's records

• Log in as two different accounts and compare results across listings/orders/messages/profiles.
• Expected result: strict ownership boundaries hold.

3. Service role never appears in client output - Verify browser bundle contains no private keys by searching built assets again after deploy prep. Expected result: zero matches for service role strings.

4. Protected Edge Functions reject missing JWTs - Call each protected function without auth headers. Expected result: 401 Unauthorized with no side effects.

5. Privileged actions require correct role claims - Test seller-only vs admin-only flows explicitly. Expected result: buyers cannot perform seller/admin actions.

6. Duplicate request handling works - Retry mutation endpoints quickly to simulate double submits and network retries. Expected result: no duplicate listings/orders/messages unless intended.

7. Error responses do not leak internals - Trigger validation failures deliberately. Expected result: no stack traces with secrets or table names exposed to end users.

8. Basic load sanity check - Run a small smoke test against login plus one protected action at around 20 to 50 concurrent requests if your MVP expects traffic spikes from ads or launch posts. Expected result: stable response times under p95 of about 300 ms for normal reads and no auth bypasses under load.

Acceptance criteria I would use:

• All sensitive tables have RLS enabled.
• All policies are least-privilege by default.
• All protected functions fail closed when unauthenticated.
• No private key exists in client code or public build output.
• Zero critical findings remain after manual verification of core flows.

Prevention

To stop this from happening again, I would put guardrails around both engineering and product workflow.

• Security review checklist before merge:

Every PR touching auth must answer three questions: who can call it, what data they can see, what happens when they fail authentication?

• Secret handling rules:

Use server-only env vars for service roles and third-party credentials. Rotate secrets quarterly at minimum and immediately after any suspected exposure.

• Database policy review:

Treat every new table as private until proven public through an explicit policy review.

• Monitoring:

Alert on spikes in unauthenticated requests, unusual writes, failed function invocations, and new admin-like activity outside business hours.

• UX guardrails:

Show clear login prompts before protected actions fail deep inside the stack, so users do not spam retry buttons when authentication expires.

• Performance guardrails:

Cache safe public reads at the edge where possible, but never cache personalized responses without a user boundary check first.

• QA gate:

Add one auth test per critical flow in CI so regressions fail before deploy, not after customers find them through broken onboarding or leaked data screenshots.

When to Use Launch Ready

Launch Ready fits when you need me to stop the bleeding fast and get the product back into a deployable state without turning it into a six-week rewrite. I handle domain setup, email deliverability basics, Cloudflare, SSL, deployment, secrets, monitoring, and handover so your MVP stops living on guesswork alone.

For this specific issue, I would use Launch Ready when you already know the app should stay alive but needs production safety now:

• exposed keys need rotation,
• auth needs tightening,
• deployment needs cleanup,
• monitoring needs to catch future failures early,
• DNS or SSL may be part of why your launch looks broken from outside the app too.

What you should prepare before I start:

• Supabase project access with owner-level permissions where possible
• Repo access plus deployment platform access
• List of all environments: local staging preview production
• Any known leaked keys that must be rotated immediately
• A short list of critical marketplace flows:

signup, to login, create listing, browse listing, message seller, checkout, admin moderation

If you bring me that package cleanly prepared, I can usually move faster than trying to untangle half-documented fixes across multiple tools while customers are already hitting the product live.

References

• https://roadmap.sh/api-security-best-practices
• https://roadmap.sh/cyber-security
• https://roadmap.sh/code-review-best-practices
• https://supabase.com/docs/guides/database/postgres/row-level-security
• https://supabase.com/docs/guides/functions/authentication

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Take the next step

If this is a problem in your product right now, here is what to do next:

• [Use the free Cyprian tools](/tools) - estimate cost, score app risk, check launch readiness, or pick the right service sprint.

• [Book a discovery call](/contact) - I will tell you honestly whether you need a sprint or if you can DIY the next step.

*Written by Cyprian Tinashe Aarons - senior full-stack and AI engineer helping founders rescue, launch, automate, and scale AI-built products.*