Security for Multi-Tenant Vibe-Coded Apps
Multi-tenant apps serve multiple organizations on shared infrastructure. The critical security requirement is absolute data isolation between tenants — a failure means one customer accesses another's data.
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Why Security Matters for Multi-Tenant Applications
Multi-tenancy is the default architecture for SaaS, and it's where AI-generated code most consistently fails at security. AI tools generate queries without tenant filters, create endpoints without tenant authorization, and build UIs that can display cross-tenant data with simple URL manipulation. A multi-tenant data breach is catastrophic because it potentially affects ALL customers simultaneously. One vulnerability = every customer's data exposed.
Security Risks
Cross-tenant data access
criticalUsers accessing data belonging to other tenants through IDOR, missing RLS, or unscoped queries.
Mitigation
Implement tenant_id on every table with RLS policies enforcing tenant scope. Add tenant context to every API request and validate it against the authenticated user's tenant.
Tenant admin privilege escalation
highAdmin of one tenant gaining system-level or cross-tenant admin access.
Mitigation
Separate tenant-admin from system-admin roles. Tenant admins manage only their tenant's users and data. System admin is a separate authentication path.
Shared resource contention
mediumOne tenant consuming disproportionate resources affecting other tenants' performance.
Mitigation
Implement per-tenant rate limits and resource quotas. Monitor usage patterns and throttle abusive tenants.
Security Checklist
Every table must have a tenant_id column with RLS policies enforcing tenant isolation.
Extract and validate tenant context from the authenticated session on every request.
Tenant administrators cannot access other tenants or system-level configuration.
Automated tests that verify data isolation by attempting cross-tenant access.
Prevent one tenant from consuming all shared resources.
Include tenant_id in all log entries for debugging and security monitoring.
Real-World Scenario
A developer builds a CRM using Lovable for multiple small businesses. Each business has their own contacts, deals, and notes. The Supabase queries use simple WHERE clauses in the frontend code to filter by tenant. An attacker removes the WHERE clause from a client-side request and downloads the contacts for every business on the platform — including phone numbers, emails, and deal values.
Frequently Asked Questions
What's the best way to implement tenant isolation?
Row Level Security (RLS) at the database level. Add tenant_id to every table and create RLS policies that automatically filter data to the current user's tenant. This enforces isolation regardless of what the application code does.
Should I use separate databases per tenant?
For most vibe-coded apps, no. RLS-based isolation in a shared database is simpler, cheaper, and sufficient. Separate databases add operational complexity. Reserve database-per-tenant for enterprise customers with strict compliance requirements.
How do I test tenant isolation?
Create two test tenants. Authenticate as Tenant A and attempt to read, update, and delete Tenant B's data through every API endpoint. Also test by modifying request parameters and database queries directly. Automate these tests.
Security for Other Use Cases
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