docs(misconf): add info about limitations for terraform plan json (#7143

)

docs/docs/coverage/iac/terraform.md

@@ -47,4 +47,33 @@ trivy conf --tf-exclude-downloaded-modules ./configs
 ```
 
 ## Secret
-The secret scan is performed on plain text files, with no special treatment for Terraform.
+The secret scan is performed on plain text files, with no special treatment for Terraform.
+
+## Limitations
+
+### Terraform Plan JSON
+
+#### For each and count objects in expression
+
+The plan created by Terraform does not provide complete information about references in expressions that use `each` or `count` objects. For this reason, in some situations it is not possible to establish references between resources that are needed for checks when detecting misconfigurations. An example of such a configuration is:
+
+```hcl
+locals {
+  buckets = toset(["test"])
+}
+
+resource "aws_s3_bucket" "this" {
+  for_each = local.buckets
+  bucket = each.key
+}
+
+resource "aws_s3_bucket_acl" "this" {
+  for_each = local.buckets
+  bucket = aws_s3_bucket.this[each.key].id
+  acl    = "private"
+}
+```
+
+With this configuration, the plan will not contain information about which attribute of the `aws_s3_bucket` resource is referenced by the `aws_s3_bucket_acl` resource.
+
+See more [here](https://github.com/hashicorp/terraform/issues/30826).