First Users Security Checklist: 12-Item Guide Before Your First Signup

TL;DR

Your first users are your most valuable. A security incident during your early days can destroy trust before you build it. 5 critical items must be verified before inviting anyone, 5 important items should be done soon, and 2 recommended items when you can. Before inviting anyone to sign up, verify authentication works, test data isolation, set up basic monitoring, and have a plan for when things go wrong.

Quick Checklist (5 Critical Items)

Test signup flow end-to-endCreate a real account and verify email confirmation works

Test logout completely clears sessionAfter logout, protected pages should redirect to login

Test cross-user data accessAs User A, try to access User B's data

Test error pages don't leak infoTrigger errors and verify stack traces aren't shown

Set up basic error monitoringSentry or similar to catch issues before users report them

Authentication Testing 4

Test signup flow end-to-endCreate a real account. Verify email confirmation works if enabled. How to test authentication flows

Test login with wrong credentialsVerify error messages don't reveal whether email exists in system. How to secure login error messages

Test password reset flowRequest reset, verify email arrives, complete reset successfully. How to secure password reset

Test logout completely clears sessionAfter logout, verify protected pages redirect to login. How to implement secure logout

Data Isolation 3

Create two test accountsSign up as User A and User B with different emails. How to test data isolation

Test cross-user data accessAs User A, try to access User B's data by modifying URLs or API calls. How to prevent IDOR vulnerabilities

Verify user list is not exposedEnsure non-admin users cannot see other users' emails or data. How to protect user data

Error Handling 3

Test error pages don't leak infoTrigger errors and verify stack traces aren't shown to users. How to secure error pages

Check API error responsesAPI errors should return appropriate messages, not internal details. How to secure API error responses

Test 404 pagesVerify 404 errors don't reveal directory structure or sensitive paths. How to secure 404 pages

Incident Preparedness 2

Set up basic error monitoringSentry, LogRocket, or similar to catch issues before users report them. How to set up error monitoring

Document your incident response planKnow how you'll respond if something goes wrong. Who to contact, what to do. How to create an incident response plan

Why First Users Matter Most

Your first users are early adopters who took a chance on you. They're more likely to forgive bugs but less likely to forgive security issues. A data leak or account compromise in your first month can spread through the communities where early adopters gather, damaging your reputation before you've established it.

Additionally, early users often provide detailed feedback. If they encounter security issues, they're more likely to tell you (and others) than users who joined later and have lower expectations of communication.

When should I run this checklist?

Run this checklist after completing your MVP security checklist, but before sharing signup links with anyone outside your team. Even "soft launches" to friends and family need basic security in place.

What if I find issues during testing?

Fix them before inviting users. Critical issues (data isolation failures, authentication bypasses) must be fixed. Minor issues can be documented and fixed soon after launch, but document them so you don't forget.

How many test accounts should I create?

At minimum two, to test data isolation. If you have different user roles (admin, regular user, etc.), create accounts for each role to test permission boundaries.

TL;DR

Quick Checklist (5 Critical Items)

Authentication Testing 4

Data Isolation 3

Error Handling 3

Incident Preparedness 2

Why First Users Matter Most

When should I run this checklist?

What if I find issues during testing?

How many test accounts should I create?

Related Articles

MVP Security Checklist

Authentication Checklist

Incident Response Checklist

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First Users Security Checklist: 12-Item Guide Before Your First Signup