Checkout problems upgrading to Magento 1.9.3.4+

Magento version 1.9.3.4 include patch SUPEE-9767 V2 which includes security patching for the checkout process.

For your current front-end templates to work with this patch you will need to include a form key value to a number of forms in the checkout process.

<?php echo $this->getBlockHtml('formkey') ?>

Load the templates below from your  app/design/frontend/<package>/<theme> directory and add the Form Key code above between the <form> and </form> tags on each.

The basic templates that will need upgraded:

• /template/checkout/cart/shipping.phtml
• /template/checkout/onepage/billing.phtml
• /template/checkout/onepage/shipping.phtml
• /template/checkout/onepage/payment.phtml

If persistant checkout is enabled:

• /template/checkout/onepage/shipping_method.phtml
• /template/persistent/checkout/onepage/billing.phtml

If you allow shippinng to multiple addresses:

• /template/checkout/multishipping/billing.phtml
• /template/checkout/multishipping/shipping.phtml