DESINFECTAR LA ENTRADA DE ARCHIVOS

function softpang_sanitize_file( $file, $setting ) {
     $mimes = array(
         'jpg|jpeg|jpe' => 'image/jpeg',
         'gif'          => 'image/gif',
         'png'          => 'image/png'
     );
     $file_ext = wp_check_filetype( $file, $mimes );
     return ( $file_ext['ext'] ? $file : $setting->default );
 }
$wp_customize->add_setting(
   'sp_urlimg_team0',
   array(
      'sanitize_callback' => 'softpang_sanitize_file'    
   )
); 

$wp_customize->add_control( 
new WP_Customize_Upload_Control( 
  $wp_customize, 
  'sp_urlimg_team0, 
   array(
       'label'      => __( 'Seleccione Imagen', 'softpang' ),
       'section' => 'sp_team0_section'                 
   )
));

DESINFECTAR LA CASILLA DE VERIFICACIÓN

function sp_sanitize_checkbox( $checked ) {
   return ( ( isset( $checked ) && true == $checked ) ? true : false);
}

$wp_customize->add_setting('sp_show_clientspanel',array(
    'default' => false,
    'sanitize_callback' => 'sp_sanitize_checkbox',
    'capability' => 'edit_theme_options',
));
$wp_customize->add_control( 'sp_show_clientspanel', array(
    'settings' => 'sp_show_clientspanel',
    'section' => 'sp_clients_section',
    'label' => __('Mostrar Seccion','softpang'),
    'type' => 'checkbox'
));

DESINFECTAR EL CÓDIGO DE COLOR HTML

function theme_slug_customizer( $wp_customize ) {          
    //your section
    $wp_customize->add_section('theme_slug_customizer_your_section',
    array(
        'title' => esc_html__( 'Your Section', 'theme_slug' ),
        'priority' => 150
    ));            
    //add setting to your section
    $wp_customize->add_setting('theme_slug_customizer_color',
    array(
        'default' => '#000000',
        'sanitize_callback' => 'sanitize_hex_color' //validates 3 or 6 digit HTML hex color code
    ));  
    $wp_customize->add_control(new WP_Customize_Color_Control(
    $wp_customize,'theme_slug_customizer_color',
    array(             
       'label'=> __( 'Your Setting with color input', 'theme_slug' ),
       'section' => 'theme_slug_customizer_your_section'       
    )));         
}
add_action( 'customize_register', 'theme_slug_customizer' );

DESINFECTAR EL CÓDIGO HTML

function theme_slug_customizer( $wp_customize ) {           
  
    //your section
        $wp_customize->add_section( 
            'theme_slug_customizer_your_section', 
            array(
                'title' => esc_html__( 'Your Section', 'theme_slug' ),
                'priority' => 150
            )
        );      
           
                   
    //add setting to your section
        $wp_customize->add_setting( 
            'theme_slug_customizer_html_code', 
            array(
                'sanitize_callback' => 'wp_kses_post' //keeps only HTML tags that are allowed in post content
            )
        );
          
        $wp_customize->add_control( 
            'theme_slug_customizer_html_code', 
            array(
                'label' => esc_html__( 'Your Setting with HTML code', 'theme_slug' ),
                'section' => 'theme_slug_customizer_your_section',
                'type' => 'textarea'
            )
        );         
       
}
add_action( 'customize_register', 'theme_slug_customizer' );

LISTA DE FUNCIONES DE DESINFECCIÓN DE WORDPRESS

También te doy algunas funciones PHP para llenar algunos vacíos.

https://divpusher.com/blog/wordpress-customizer-sanitization-examples/