CCSS (Common Configuration Scoring System) is a set of measures used to determine the severity of the rule.
Each rule is associated with a high-level category. For example IAM, Container, Monitoring, Logging, Network, etc.
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Test your applicationsUsing a wildcard in the principal element of a trust policy allows anyone in any account to assume the role. A principal ARN of arn:aws:iam::123456789012:root or 123456789012 allows anyone in the 123456789012 account to assume the role.
Set Principal attribute to a specific principal, e.g. arn:aws:iam::123456789012:role/role-name.
Example configuration:
resource "aws_iam_role" "test_role" {
  name = "test_role"
  assume_role_policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": "sts:AssumeRole",
      "Principal": {
        "AWS": "arn:aws:iam::123456789012:role/my-role"
      },
      "Effect": "Allow",
      "Sid": ""
    }
  ]
}
EOF
}
Set Principal in Properties.AssumeRolePolicyDocument attribute to a specific principal, e.g. arn:aws:iam::1234:role/role-name.