Source

File: wp-includes/class-wp-customize-widgets.php

public function sanitize_widget_instance( $value ) {
		if ( array() === $value ) {
			return $value;
		}

		if ( empty( $value['is_widget_customizer_js_value'] )
			|| empty( $value['instance_hash_key'] )
			|| empty( $value['encoded_serialized_instance'] ) ) {
			return;
		}

		$decoded = base64_decode( $value['encoded_serialized_instance'], true );
		if ( false === $decoded ) {
			return;
		}

		if ( ! hash_equals( $this->get_instance_hash_key( $decoded ), $value['instance_hash_key'] ) ) {
			return;
		}

		$instance = unserialize( $decoded );
		if ( false === $instance ) {
			return;
		}

		return $instance;
	}