In the Automattic WooCommerce plugin before 3.2.4 for WordPress, an attack is possible after gaining access to the target site with a user account that has at least Shop manager privileges. The attacker then constructs a specifically crafted string that will turn into a PHP object injection involving the includes/shortcodes/class-wc-shortcode-products.php WC_Shortcode_Products::get_products() use of cached queries within shortcodes.
https://woocommerce.wordpress.com/2017/11/16/woocommerce-3-2-4-security-fix-release-notes/