I am sure this has been requested more than once.
Here's how you can achieve this.
Consider user Admin (usually id 1) or any other user.
We can create a default media set which would comprise of all the uploaded by this user.
remove_filter('posts_where', 'wplms_attachments_wpquery_where');
add_filter( 'posts_where', 'wplms_default_media_set');
function wplms_default_media_set( $where ){
$instructor_privacy = vibe_get_option('instructor_content_privacy');
if(isset($instructor_privacy) && $instructor_privacy && !current_user_can('manage_options')){
if( is_user_logged_in() && current_user_can('edit_posts')){
global $current_user;
if( isset( $_POST['action'] ) ){
if( $_POST['action'] == 'query-attachments' ){
$where .= ' AND post_author IN ('.$current_user->data->ID.',1 )'; //1 is the user id of default user for media set
}
}
}
}
return $where;
}