The fix to this issue is because the form key validation is missing on check out. You can view the fix here How to fix Magento checkout after upgrading
How to fix Magento checkout redirecting to cart after upgrading to 1.9.3.3 or 1.9.3.4The fix to this issue is because the form key validation is missing on check out. You can view the fix here How to fix Magento checkout after upgrading
