How are add_on versions computed

I am using Terraform to provision some EKS addons and I can’t find how the addon versions (if left blank) are determined. For example when I run terraform apply without addon_name defined in my .tf file:

resource "aws_eks_addon" "vpc-cni" {
  cluster_name      = var.cluster_name
  addon_name        = "vpc-cni"
  resolve_conflicts = "OVERWRITE"
  provider          = aws.cluster_account
  # addon_version     = "v1.8.0-eksbuild.1"
}

I get this result:

  # aws_eks_addon.vpc-cni will be created
  + resource "aws_eks_addon" "vpc-cni" {
      + addon_name        = "vpc-cni"
      + addon_version     = (known after apply)
      + arn               = (known after apply)
      + cluster_name      = "eks-test"
      + created_at        = (known after apply)
      + id                = (known after apply)
      + modified_at       = (known after apply)
      + resolve_conflicts = "OVERWRITE"
      + tags_all          = (known after apply)
    }

After applying this change, version v1.7.5-eksbuild.2 of vpc-cni is running on my cluster. This isn’t the latest compatible version. Do I need to manage updates in the EKS console myself? Should I just be defining the version I want installed during each terraform apply?