SaaS Security Checklist: 20-Item Guide for Multi-Tenant Apps

TL;DR

This 20-item checklist covers the most critical security issues in SaaS and multi-tenant applications: tenant isolation, data encryption, and enterprise authentication. 7 critical items must be fixed before launch, 9 important items within the first week, and 4 recommended items when you can.

Quick Checklist (5 Critical Items)

Implement row-level securityEvery database query must be scoped to the current tenant

Test cross-tenant accessVerify one tenant cannot access another's data through any endpoint

Encrypt data at restEnable database encryption for all customer data

Encrypt data in transitUse TLS 1.2+ everywhere with HSTS headers

Validate all API inputsValidate types, lengths, formats, and ranges on every endpoint

Tenant Isolation 5

Implement row-level securityEvery database query must be scoped to the current tenant. Use RLS policies or add tenant_id to every query. How to implement tenant isolation

Test cross-tenant accessCreate test accounts in different tenants. Verify one cannot access the other's data through any endpoint. How to test tenant isolation

Isolate file storageUser uploads must be stored with tenant prefixes. Verify URLs cannot be manipulated to access other tenants. How to isolate file storage

Separate background jobs by tenantEnsure queued jobs cannot process data from wrong tenants. Include tenant context in job payloads. How to secure background jobs

Log tenant context alwaysEvery log entry should include tenant ID. This enables tenant-specific debugging and audit trails. How to implement audit logging

Authentication and Authorization 5

Support SSO for enterprise customersImplement SAML or OIDC support. Enterprise customers often require single sign-on integration. How to implement SSO

Implement organization-level permissionsUsers belong to organizations with roles. Define clear permission boundaries between admin, member, and viewer. How to implement RBAC

Require strong passwords or passwordlessEnforce minimum password requirements or offer magic links and social login as alternatives. How to implement password policy

Support organization-enforced 2FAAllow organization admins to require 2FA for all members. Track compliance status per user. How to implement 2FA

Implement session managementShow active sessions, allow users to revoke sessions, and support admin forced logout. How to implement session management

Data Security 4

Encrypt data at restEnable database encryption. Most cloud providers offer this by default but verify it is enabled. How to encrypt data at rest

Encrypt data in transitUse TLS 1.2+ everywhere. Enforce HTTPS with HSTS headers and secure cookies. How to configure TLS

Implement data retention policiesDefine how long you keep data. Allow customers to export and delete their data on request. How to implement data retention

Set up audit loggingLog all data access and modifications. Include who, what, when, and from where. How to implement audit logging

API Security 3

Implement rate limiting per tenantPrevent one customer from affecting others. Set limits on API calls, uploads, and resource-intensive operations. How to implement rate limiting

Validate all API inputsValidate types, lengths, formats, and ranges. Reject malformed requests early. How to validate API inputs

Support API key managementLet customers generate and revoke API keys. Show last used timestamps and support key rotation. How to implement API keys

Compliance Preparation 3

Document your security practicesCreate a security page for your website. Enterprise buyers will ask for documentation. How to create a security page

Prepare for security questionnairesPre-answer common questions about encryption, access controls, and incident response. How to answer security questionnaires

Plan for SOC 2 certificationIf targeting enterprise customers, plan your SOC 2 Type II timeline. Start collecting evidence early. How to prepare for SOC 2

Multi-Tenancy Architecture Matters

The biggest SaaS security risk is tenant data leakage. One customer accessing another customer's data can end your business. Design tenant isolation into your architecture from day one. Retrofitting it later is painful and error-prone.

Row-level security in your database is the foundation. But also check file storage, background jobs, caches, and logs. Tenant context should flow through your entire stack.

What is tenant isolation in SaaS?

Tenant isolation ensures one customer cannot access another customer's data. This can be achieved through separate databases per tenant, row-level security policies, or schema separation within a shared database.

Does a SaaS app need SOC 2 compliance?

SOC 2 is not legally required, but enterprise customers often require it. If you plan to sell to mid-market or enterprise companies, budget for SOC 2 Type II certification within your first 2 years.

How do I handle customer data deletion requests?

Build data export and deletion features early. When a customer requests deletion, remove their data from active databases, backups (within retention windows), logs, and any third-party services. Document your process for compliance.