Can't set tenant properties anymore

Target SharePoint environment

SharePoint Online

What SharePoint development model, framework, SDK or API is this about?

💥 SharePoint REST API

Describe the bug / error

Blocked Custom scripts blocking us from setting Tenant Properties. We're using Tenant Properties as global settings for our apps, e.g. to disable telemetry.

I wonder if that's intended?

Steps to reproduce

Assuming you have permissions to set tenant properties.

1. Enable Custom scripts block on your site/app catalog site (technically this should now be automatically enforced)
2. Try to set tenant properties, e.g.

fetch("<appCatalogUrl>/_api/web/SetStorageEntity", {
  "headers": {    
    "content-type": "application/json;charset=utf-8"
  },  
  "body": "{\"key\":\"Test\",\"value\":\"TEST\"description\":\"TEST\",\"comments\":\"TEST\"}",
  "method": "POST"
});

3. Request fails with status code 403

{
    "error": {
        "code": "-2147024891, System.UnauthorizedAccessException",
        "message": "Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))"
    }
}

Expected behavior

Tenant property is set