save_post action firing before I publish / save the post

I’m trying to update a posts meta only after it has been saved or updated.

My function is pretty simple

function update_test( $post_id ) {

  update_post_meta($post_id, 'copied', '1');
  update_post_meta($post_id, 'blurb', 'this value updated by save_post action');

}

add_action( 'save_post', 'update_test');

When I add a new post at wp-admin/post-new.php I can see the two custom fields values have already been updated. The fields themselves exist with Advanced Custom Fields. But shouldn’t be updated until after the post has been published / saved and or updated. Why is this updating the fields as soon as the post-new.php form loads?

A draft or “blank” is saved as soon as you start to create a new post. Those new posts have the post_status of auto-draft. Check for that to prevent your callback from firing on those “blank” post saves.

function update_test( $post_id, $post ) { 
  if (isset($post->post_status) && 'auto-draft' == $post->post_status) {
    return;
  }
  update_post_meta($post_id, 'copied', '1');
  update_post_meta($post_id, 'blurb', 'this value updated by save_post action');
}
add_action( 'save_post', 'update_test', 1, 2);

You may also want to check for the DOING_AJAX and DOING_AUTOSAVE constants.