Redshift Serverless namespaces should not use the default admin username

How to fix it

Change the namespace's admin username to something an attacker would not guess. The username and the password have to be updated in the same call, so treat this as a credential rotation and update any application, BI tool or scheduled job that signs in with the old credentials. The check flags admin, awsuser, root, sa, oracle and postgres, which is broader than AWS's own control.

In the console

Redshift Serverless → Namespace configuration → the namespace → Actions → Edit admin credentials

With the AWS CLI

aws redshift-serverless update-namespace --namespace-name <namespace-name> --admin-username <admin-username> --admin-user-password <admin-user-password> --region <region>

With Terraform

resource "aws_redshiftserverless_namespace" "this" {
  namespace_name = var.namespace_name
  admin_username = var.admin_username
}