After you've upgraded to Magento version 1.9.3.4 have you noticed that your check out just sits on billing information and doesn't proceed to the shipping options? Apparently, the Magento team discovered a security issue and added form key validation on check out. Form keys help prevent Cross Site Request Forgery attacks on Magento forms. Cross Site Request Forgery is the attempt of submitting malicious form information from one website to another. (In lamen's terms) Form keys are a way for a website to validate that the form submission is being sent within itself. In the Magento world, in order to create any custom forms, they must have a form key. If not, the Magento action controller will not respond. Well, there are 3 options to resolve this issue. It's understandable that this will result in lost revenue. If you have to keep your online store running and cannot wait for a web developer to resolve the issue. Navigate to System -> Configuration. On the left column, scroll all the way down to Advanced -> Admin. In the collapse, select security and set "Enable Form Key Validation On Checkout" to No. Broken checkout after Magento upgrade That should solve your issue. Please do leave a comment if you have any questions. ThanksWhat are form keys?
How do I fix it?