After updating WooCommerce to 3.0, clicking the Add to Cart button on a grouped product page led to an error page in Chrome that said:

This page isn’t working

Chrome detected unusual code on this page and blocked it to protect your personal information (for example, passwords, phone numbers, and credit cards).
Try visiting the site’s homepage.

Here’s a screenshot:

First, I looked through all the template files that needed updating by going to: WooCommerce > System Status > Templates and saw that the file woocommerce/single-product/add-to-cart/grouped.php was out of date (along with many others).

I replaced the grouped.php file with the latest WooCommerce version of that file and the site started working properly again.

There really should be a better way of customizing WooCommerce files so that you don’t need to worry about a site breaking every time you update the plugin!