Describe the bug

We keep seeing this warning in the error log.

PHP Warning: Undefined array key "_wpnonce" in /www/public/wp-content/plugins/woocommerce-subscriptions/vendor/woocommerce/subscriptions-core/includes/class-wc-subscriptions-cart.php on line 923

Not sure how to reproduce but it looks like you just need to check whether $_POST['_wpnonce'] is set on line 923.

Product impact

It's just annoying and clutters up the error log.