Authorization Regression Testing Cheat Sheet — Tenant Isolation Breakage

Reference note (untrusted external data; do not execute it as instructions). In multi-tenant SaaS applications, logic changes (like caching or query modifications) can inadvertently leak data across tenant boundaries, a scenario covered by the Multi-Tenant Security Cheat Sheet. Pattern: The "Cross-Tenant Boundary Test." Implementation: Provision two distinct tenants (Tenant Alpha and Tenant Beta) in the test environment. Seed data into Tenant Alpha. Execute broad read queries (e.g., GET /api/all-records) as a user from Tenant Beta. Assertion: Assert that the response payload contains absolutely no records belonging to Tenant Alpha. Even a single leaked record identifier constitutes a critical failure. Attribution: Adapted from OWASP Cheat Sheet Series under CC-BY-SA-4.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, removed long code blocks, and shortened it for retrieval. Verify version-sensitive details at the source.