How I Would Fix exposed API keys and missing auth in a Circle and ConvertKit waitlist funnel Using Launch Ready.

How I Would Fix exposed API keys and missing auth in a Circle and ConvertKit waitlist funnel Using Launch Ready

The symptom is usually ugly but simple: the waitlist page works, but the API keys are visible in the browser, the signup endpoint can be hit without any auth, and you start seeing spam signups, duplicate contacts, or unexpected email sends. In business terms, this means leaked secrets, broken lead quality, higher support load, and a real chance of getting your Circle or ConvertKit account rate-limited or flagged.

The most likely root cause is that the funnel was built fast with client-side calls directly to third-party APIs, often from a Lovable, Cursor, or custom React app that never got a proper backend layer. The first thing I would inspect is the browser network tab and the deployed frontend bundle to confirm whether secrets are embedded in JavaScript or exposed in request headers.

Triage in the First Hour

1. Check the live page in an incognito browser.

• Submit the waitlist form once.
• Open DevTools and inspect the Network tab.
• Confirm whether requests go directly to Circle or ConvertKit from the browser.

2. Search the frontend bundle for secrets.

• Look for API keys, private tokens, webhook secrets, and environment variable names.
• If you see anything like `pk_`, `sk_`, `api_key`, `secret`, or a full token string in shipped JS, treat it as exposed.

3. Review deployment logs.

• Check Vercel, Netlify, Cloudflare Pages, Render, or whatever is hosting the funnel.
• Look for recent deploys that may have accidentally baked env vars into client code.

4. Inspect Circle and ConvertKit dashboards.

• Review recent API usage.
• Check for unusual signup spikes, duplicate subscribers, bounced emails, or webhook failures.
• Confirm whether any public forms are accepting submissions without validation.

5. Audit auth and access paths.

• Identify every route that creates leads or syncs data.
• Verify whether there is any server-side verification at all.
• Confirm whether rate limiting exists on form submit endpoints.

6. Check DNS and email settings if the funnel sends email.

• Verify SPF, DKIM, and DMARC records.
• Confirm sending domains are correct and not spoofable.

7. Freeze risky changes.

• Stop new feature work until secrets are rotated and auth is fixed.
• If needed, temporarily disable public submission routes while preserving landing page traffic.

## Quick local check for exposed secrets in a built app
grep -RniE "sk_|pk_|api[_-]?key|secret|token" dist build .next out

Root Causes

| Likely cause | What it looks like | How I confirm it | |---|---|---| | Client-side API calls to ConvertKit or Circle | Keys appear in browser requests or bundled JS | Inspect Network tab and built assets | | Missing server-side auth gate | Anyone can POST to signup endpoint | Try submitting without a session or token | | Secrets stored in frontend env vars | Build injects sensitive values into public code | Review `.env`, build config, and framework env naming | | Webhook endpoint left open | Third parties can trigger lead creation | Check whether webhook signature validation exists | | No input validation | Spam emails or malformed data enter CRM | Test invalid payloads and look at stored records | | Weak deployment hygiene | Old builds still contain old keys | Compare current deploy with previous releases |

The most common issue I see is this: founders think "environment variables" automatically means secure. In reality, anything exposed to browser code is public by design. If the app needs a secret to talk to Circle or ConvertKit, that secret belongs on the server only.

The Fix Plan

1. Move all secret-dependent logic server-side.

• Create a small backend route or server action that receives only sanitized form fields like name and email.
• That backend should call Circle or ConvertKit using private environment variables stored only on the server.

2. Rotate every exposed key immediately.

• Assume any key shipped to the browser is compromised.
• Revoke old ConvertKit tokens, Circle credentials, webhook secrets, and any related service tokens.
• Generate new ones and update only server-side env vars.

3. Add real request validation before creating leads.

• Validate email format, required fields, length limits, and allowed characters.
• Reject empty submissions and suspicious payload sizes.
• Normalize input before storing it.

4. Add an auth control for sensitive actions.

• If there is an admin panel or internal lead sync route, protect it with session auth or signed tokens.
• Do not rely on hidden URLs alone.
• For public waitlist forms, use anti-abuse controls instead of pretending they are private.

5. Add rate limiting and abuse protection.

• Rate limit by IP and by fingerprinted session where appropriate.
• Put Cloudflare WAF rules in front of public endpoints if available.
• Add basic bot mitigation on form submits.

6. Validate webhooks if they are part of the flow.

• Require signature verification on inbound webhooks from ConvertKit or any automation tool.
• Reject unsigned requests immediately.

7. Clean up deployment config.

• Remove secrets from frontend env files such as `.env.local` if they are referenced by client code.
• Confirm only safe values are exposed with public prefixes like `NEXT_PUBLIC_` when using Next.js style stacks.
• Rebuild from scratch after rotation so no stale artifact survives.

8. Harden email deliverability while you are here.

• Set SPF, DKIM, and DMARC correctly for your sending domain.
• Make sure redirects and tracking links do not break authentication flows between Circle and ConvertKit.

My preferred path is boring on purpose: one thin server endpoint for lead capture, one private secret store for credentials, one validation layer before third-party writes. That keeps the fix small enough to ship in 48 hours without turning a funnel rescue into a full rewrite.

Regression Tests Before Redeploy

Before I ship this back live, I want proof that the leak is gone and that lead capture still works end to end.

1. Secret exposure checks

• Confirm no API keys appear in built assets or source maps.
• Confirm no secrets appear in browser Network requests except non-sensitive public identifiers where expected.

2. Auth checks

• Attempt submission without any session cookie or token if auth is required for admin routes.
• Confirm unauthorized requests return 401 or 403 where appropriate.

3. Input validation checks

• Submit valid email addresses from Gmail and corporate domains.
• Submit malformed emails like `test@`, empty strings, very long strings, and HTML tags.
• Confirm invalid inputs are rejected cleanly.

4. Abuse checks

• Fire multiple rapid submissions from one IP to confirm rate limits work.
• Confirm spammy repeats do not create duplicate contacts downstream.

5. Third-party integration checks

• Verify one successful signup reaches both Circle and ConvertKit if both are supposed to receive it.
• Check no duplicate records are created unless intended logic says otherwise.

6. UX checks

• Confirm loading states show during submission so users do not double-click submit buttons.
• Confirm error states tell users what happened without leaking internal details.

7. Rollback check

• Make sure you can revert to the previous deploy if something breaks after rotation.

Acceptance criteria I would use:

• Zero exposed secrets in frontend code or browser-visible responses.
• 100 percent of lead writes go through server-side validation first.
• Unauthorized access returns 401/403 consistently on protected routes.
• No more than 1 duplicate lead per 100 test submissions under normal conditions.
• Form submit p95 stays under 500 ms excluding third-party latency where possible.

Prevention

I would put guardrails around this so it does not happen again after launch week panic fades out.

• Monitoring
• Set alerts for unusual signup volume spikes and repeated failed requests.
• Monitor p95 latency on form submits so slow integrations do not silently fail conversions.
• Watch webhook failure counts daily during the first week after release.

• Code review
• Never approve client-side code that contains private API credentials.
• Review every change touching auth routes, env vars, webhooks, redirects, and form handlers first.

• Security

Delivery Map

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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.*