Launch Ready API security Checklist for AI-built SaaS app: Ready for security review in B2B service businesses?.

Launch Ready API Security Checklist for AI-built SaaS app: Ready for security review in B2B service businesses?

For an AI-built SaaS app in a B2B service business, "ready" does not mean "it works on my laptop." It means a security reviewer can test the product without finding exposed secrets, broken auth, weak tenant isolation, unsafe CORS, or a deployment setup that can be taken down by a bad config change.

If I were auditing this for launch, I would want to see three things before I call it ready:

• No critical auth bypasses or exposed credentials.
• API requests are authenticated, authorized, validated, logged, and rate-limited.
• The production environment is deployed with proper DNS, SSL, email authentication, monitoring, and rollback paths.

For a founder self-assessment, the bar is simple: if a reviewer can create data they should not see, access another customer's records, or find a secret in code or logs, you are not ready. If your p95 API latency is over 500ms on core flows, or your app has no uptime monitoring and no alerting path, you are also not ready because support load and downtime will show up immediately after launch.

Launch Ready is the right fix when the product is close but the launch layer is incomplete.

Quick Scorecard

| Check | Pass criteria | Why it matters | What breaks if it fails | |---|---|---|---| | Auth enforced on every API route | No public write endpoints unless intended | Stops unauthorized access | Data leaks, account takeover | | Authorization checked per tenant/resource | Users only see their own org data | Prevents cross-customer exposure | B2B trust failure | | Secrets removed from repo and client bundle | Zero exposed secrets in code or build output | Protects third-party systems | Credential theft | | Input validation on all write endpoints | Invalid payloads rejected with clear errors | Stops injection and bad data | Broken records, abuse | | Rate limiting on login and high-risk APIs | Abuse gets throttled or blocked | Reduces brute force and scraping | Support spikes, outages | | CORS restricted to known origins | Only approved domains can call browser APIs | Prevents browser-based abuse | Data exfiltration via web apps | | TLS active with valid SSL certs | HTTPS everywhere with no mixed content | Protects traffic in transit | Browser warnings, dropped trust | | DNS and redirects correct | Root domain and subdomains resolve properly | Avoids broken onboarding and email links | Lost traffic and failed logins | | SPF/DKIM/DMARC passing | Email auth aligned and verified | Improves deliverability and trust | Emails land in spam | | Monitoring alerts working | Uptime checks send alerts within minutes | Detects outages before customers do | Hidden downtime and churn |

The Checks I Would Run First

1. Authentication coverage on every route

The signal I look for is simple: any route that reads or changes customer data must require auth by default. If I can hit a private endpoint without a session token or valid bearer token, that is an immediate fail.

My method is to inspect the API routes directly with Postman or curl while logged out, then repeat with an expired token and a low-privilege user. I also check whether middleware protects both page routes and API routes because AI-built apps often secure one layer but forget the other.

The fix path is to centralize auth middleware first, then explicitly mark only public endpoints as public. I would rather block one extra route by mistake than ship one exposed endpoint to production.

2. Tenant isolation and object-level authorization

The signal here is whether one customer can guess another customer's record ID and retrieve it. In B2B SaaS this is where security reviews fail fast because reviewers test horizontal access by changing IDs in requests.

I test this by creating two test tenants and attempting read/write operations across both. I also check list endpoints because leaks often happen there first through filters that are too broad.

The fix path is object-level authorization on every query and mutation. In practice that means checking `user_id`, `org_id`, or `tenant_id` at the database query layer instead of trusting frontend state.

3. Secrets handling across repo, runtime, and logs

The signal is zero exposed secrets in Git history, environment files committed to the repo, client-side bundles, error logs, or preview deployments. One leaked Stripe key or webhook secret can become an incident within hours.

I use secret scanning in GitHub plus a quick manual pass through `.env`, build output, server logs, analytics tags, and CI variables. I also verify that production secrets are rotated if they were ever committed anywhere visible.

The fix path is to move all secrets into environment variables managed by the host or secret manager. Never ship secrets into frontend code; if the browser needs something sensitive to work correctly, the architecture needs redesigning.

4. CORS policy and browser trust boundaries

The signal I want is a narrow allowlist of exact origins with no wildcard unless the endpoint is truly public. If `Access-Control-Allow-Origin: *` appears on authenticated APIs with credentials enabled anywhere near them, that deserves immediate attention.

I validate this by testing requests from approved domains and from an unapproved origin in DevTools or curl with Origin headers set manually. This catches browser-exposed APIs that may still look fine from server-side tests.

The fix path is strict origin allowlisting plus separate rules for public assets versus authenticated APIs. If you use multiple subdomains like `app`, `api`, `help`, or `admin`, each one should be intentional rather than inherited by accident.

5. Rate limits on login, password reset, OTPs, and expensive endpoints

The signal is whether repeated requests get throttled before they become abuse. Login forms without rate limits invite brute force attempts; search endpoints without limits invite scraping; expensive AI calls without limits invite bill shock.

I test this by firing repeated requests against login and high-cost endpoints until throttling kicks in. I also check whether limits are per IP only or also per account because IP-only controls are weak behind shared networks.

The fix path is layered rate limiting at the edge plus application-level throttles for sensitive routes. For B2B tools I usually recommend stricter controls on auth flows than on read-only public content.

6. Production observability: logs, uptime checks, alerting

The signal here is whether you can tell when something breaks within minutes instead of hearing from customers first. A secure app without monitoring still becomes a support problem after launch because failures look like "the system just stopped working."

I check for uptime monitors on the main domain plus key API health endpoints. Then I verify error logging includes enough context to debug but never includes secrets or full tokens.

The fix path is basic but non-negotiable: uptime monitoring at 1-minute intervals for critical pages plus alerting to email or Slack. For core APIs I want p95 latency under 500ms for normal business traffic so slowdowns show up before users churn.

## Example production env pattern
DATABASE_URL=...
JWT_SECRET=...
STRIPE_SECRET_KEY=...
NEXT_PUBLIC_API_URL=https://api.example.com

Red Flags That Need a Senior Engineer

• You have multiple customer tenants but no clear tenant ID strategy in queries.
• Secrets were ever committed to GitHub or pasted into frontend environment files.
• The app uses AI-generated backend code with no auth middleware review.
• There are custom webhooks but no signature verification.
• You cannot explain who gets access to what when an admin switches accounts or resets passwords.

These are not cosmetic issues. They create real business risk: failed security review delays launch by weeks, broken onboarding increases support load immediately after ads go live, and one cross-tenant leak can kill trust with your first serious customers.

If any two of these show up together, DIY becomes false economy quickly. At that point buying Launch Ready is cheaper than paying for emergency cleanup after a bad review or customer escalation.

DIY Fixes You Can Do Today

1. Rotate any secret you have ever pasted into chat tools or shared docs.

• Assume anything manually copied around has been exposed.
• Replace it before anyone else finds it.

2. Turn on SPF DKIM DMARC for your sending domain.

• This improves deliverability for invoices, password resets, onboarding emails.
• Aim for all three passing before launch emails go out.

3. Remove wildcard CORS from authenticated routes.

• Replace it with exact domains only.
• Test both main domain and subdomains explicitly.

4. Add basic rate limiting to login and reset-password flows.

• Even simple throttles reduce brute force risk fast.
• Start stricter now; relax later if needed based on real usage.

5. Verify SSL works end-to-end across root domain and subdomains.

• Check redirects from HTTP to HTTPS.
• Make sure there are no mixed-content warnings in the browser console.

Where Cyprian Takes Over

When founders come to me after doing half of this themselves, the missing pieces usually map cleanly into Launch Ready deliverables:

| Failure found in checklist | What I do in Launch Ready | Timeline | |---|---|---| | DNS misconfigurations or broken subdomains | Fix records, redirects, root/apex routing | Hours 1-8 | | No SSL or mixed-content issues | Install SSL properly through Cloudflare/host setup | Hours 1-8 | | Weak email deliverability | Configure SPF/DKIM/DMARC correctly | Hours 4-12 | | Exposed secrets or bad env handling | Move secrets into production-safe env vars + rotate where needed | Hours 4-16 | | Missing monitoring/alerts | Set uptime checks plus alert routing for core endpoints | Hours 8-20 | | Unsafe deployment setup | Deploy production build safely with handover notes + rollback checklist | Hours 12-36 | | Cache/CDN gaps causing slow pages or overload risk | Enable caching where appropriate through Cloudflare rules/settings | Hours 16-36 | | No final launch handover documentation | Deliver checklist covering access points, keys removed from codebase boundaries reviewed) |> Hours 36-48 |

My recommendation: do not try to solve deployment hardening while also debugging product logic at the same time. That slows launch down and increases regression risk because every change touches auth behavior differently across frontend hosting backend hosting email delivery and monitoring setup.

Launch Ready exists for exactly this stage: you already have something working enough to sell internally but not yet safe enough to expose to customers or reviewers.

Delivery Map

References

• roadmap.sh Code Review Best Practices: https://roadmap.sh/code-review-best-practices
• roadmap.sh API Security Best Practices: https://roadmap.sh/api-security-best-practices
• roadmap.sh Cyber Security: https://roadmap.sh/cyber-security
• OWASP API Security Top 10: https://owasp.org/www-project-api-security/
• Cloudflare SSL/TLS documentation: https://developers.cloudflare.com/ssl/

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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.*