So I've just patched both of our Magento sites. Both sites are using custom themes, the first site went smoothly, I only needed to add the form key to one template file. The other is turning out to be an issue.
While we are using a custom theme for both websites, we are using Magento's base payment.phtml file for the onepage checkout. The file was updated by the patch, and the form key is now in the code, but for some reason the form key still fails to show up when I view the source after the page has rendered. I had to manually add the form key to two of the template files, neither of which are payment.phtml. Any idea what could be causing this?
Nevermind! I just checked out this thread https://community.magento.com/t5/Security-Patches/Checkout-Stuck-on-Step-4-after-SUPEE-9767-with-For...
The title of that thread says Step 4 which for us is Shipping Method. I should've read the entire thread first before starting a new one! The last reply by dvwb2 solved the issue.