Multitenant SaaS is a cloud application model in which many customers use the same underlying software and infrastructure, while the service keeps each customer’s data and actions logically separated. The separation is enforced by controls such as tenant IDs, access checks, routing rules, and policy settings, rather than by giving each customer a fully separate deployment.
This design is efficient and easy to scale, but it makes tenant isolation a critical security boundary. If an attacker finds a cross-tenant flaw, they may be able to read another customer’s data, trigger actions in the wrong environment, or bypass authorization between organizations. Defenders focus on strict identity validation, approved cross-tenant connections, safe connector behavior, and careful configuration of allowlists and exceptions. In multitenant SaaS, a small boundary failure can have a large impact because one shared service serves many victims at once.