preventUserExistenceErrors

When ENABLED, suppresses messages that might indicate a valid user exists when someone attempts sign-in. This parameters sets your preference for the errors and responses that you want Amazon Cognito APIs to return during authentication, account confirmation, and password recovery when the user doesn't exist in the user pool. When set to ENABLED and the user doesn't exist, authentication returns an error indicating either the username or password was incorrect. Account confirmation and password recovery return a response indicating a code was sent to a simulated destination. When set to LEGACY, those APIs return a UserNotFoundException exception if the user doesn't exist in the user pool.

Defaults to LEGACY.