As described on Magento's website: http://www.magentocommerce.com/wiki/4_-_themes_and_template_customization/catalog/adding_a_product_to_the_cart_via_querystring
Background: Performed an upgrade from CE 1.7 to 188.8.131.52. Everything else seems to be working fine after following standard procedures (http://www.magentocommerce.com/knowledge-base/entry/ce18-and-ee113-upgrading).
Tried to setup a few links that takes the user to the shopping cart and automatically adds the product to cart. Nothing outside of that; our old methods (e.g. www.website.com/checkout/cart/add?product=8&qty=1&coupon=save25) have stopped working and the user is redirected to an empty cart. I'm not even sure how to troubleshoot this problem. Any advice?