A regression check is a test that confirms a new change has not broken existing features, security controls, or expected behavior. In software security work, this is especially important after applying a patch, refactoring code, or using an AI-assisted fix, because a change that closes one vulnerability can accidentally open another path or disable a protection.
Regression checks matter because defenders need speed without losing trust in the system. They are commonly done with automated test suites, unit tests, integration tests, and security validations that compare the new build against known-good behavior. In real workflows, a regression check can catch issues like broken authentication logic, changed access control, failed input validation, or service instability after remediation. Good regression coverage helps teams patch quickly while keeping the application and its defenses intact.