Ensure Secrets are not exposed in customData used in Azure Virtual Machine

Secrets are exposed in Azure Virtual Machine customData, this may lead to unauthorized access, privilege escalation and other issues.

Once a Virtual Machine is created in the console, custom data cannot be changed. You could choose to create a new virtual machine instance, or use a virtual machine scale set which does have the ability to change update custom data.

In Terraform -
Deprecated in favor of azurerm_linux_virtual_machine and azurerm_windows_virtual_machine:

1. In the azurerm_virtual_machine resource, remove custom_data.

References:
https://learn.microsoft.com/en-us/azure/virtual-machines/custom-data
https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/virtual_machine#custom_data