Small drop-in plugin to fix double-serialized product attributes (they are no longer double-unserialized in WC Core)

	<?php
	/**
	* Plugin Name: Double serialized attributes fixer
	* Description: Adds a tool to fix double serialized attributes in WooCommerce.
	* Version: 0.0.9
	* Author: Mike J
	* Requires at least: 4.4
	* Tested up to: 4.7
	*/
	if ( ! defined( 'ABSPATH' ) ) {
	exit;
	}

	add_filter( 'woocommerce_debug_tools', 'double_serialized_attributes_fixer_tool' );

	function double_serialized_attributes_fixer_tool( $tools ) {
	$tools[ 'double_serialized_attributes_fixer' ] = array(
	'name' => 'Double-serialized attributes',
	'button' => 'Fix double-serialized attributes',
	'desc' => 'This tool will attept to fix all double-serialized attributes for products.',
	'callback' => 'double_serialized_attributes_fixer',
	);
	return $tools;
	}

	// Fixes double-serialised values – #14824.
	function double_serialized_attributes_fixer() {
	global $wpdb;

	$product_ids = wp_parse_id_list( $wpdb->get_col( "SELECT ID FROM {$wpdb->posts} WHERE post_type = 'product';" ) );

	foreach ( $product_ids as $product_id ) {
	$attributes = get_post_meta( $product_id, '_product_attributes', true );

	if ( is_serialized( $attributes ) ) {
	$attributes = maybe_unserialize( $attributes );
	update_post_meta( $product_id, '_product_attributes', $attributes );
	}
	}
	}