Ephemeral environments are temporary test environments created for a specific change and torn down after use. They are often built from infrastructure-as-code or CI/CD automation, so each branch or pull request gets its own isolated copy of the application stack, database, and supporting services.
In cyber security, they matter because they reduce contention on shared staging systems and let teams validate risky changes faster without exposing unfinished code to production users. They are especially useful for testing authentication, access control, tenant isolation, and security controls in conditions that resemble production. Defenders also use them to run scans, integration tests, and rollback checks safely. The main risk is misconfiguration: if an ephemeral environment is exposed, granted excessive credentials, or not destroyed properly, it can become a short-lived but real attack surface.