- $customize_background_url = add_query_arg( 'autofocus[control]', 'background_image', $customize_url );
- $submenu['themes.php'][20] = array( __( 'Background' ), $appearance_cap, $customize_background_url, '', 'hide-if-no-customize' );
+ $customize_background_url = add_query_arg( array( 'autofocus' => array( 'control' => 'background_image' ) ), $customize_url );
+ $submenu['themes.php'][20] = array( __( 'Background' ), $appearance_cap, esc_url( $customize_background_url ), '', 'hide-if-no-customize' );