Изменение пароля от WordPress
// Get current logged-in user.
$user = wp_get_current_user();
// Change password.
wp_set_password($new_password, $user->ID);
// Log-in again.
wp_set_auth_cookie($user->ID);
wp_set_current_user($user->ID);
do_action('wp_login', $user->user_login, $user);
Thoughtful Tapir