Magento 2.3 — Invalid Form Key. Please refresh the page

Question

Getting Invalid Form Key. Please refresh the page error not able to do any action after upgrade of Magento 2.2.5 to Magento 2.3.

Answer 1

Finally I got the solution

I have a custom payment method that uses the cc-form to take credit card payments with and without 3dsecure. After placing order with 3dsecure, I am re-directing to 3dsecure page as normal, but on returning from 3dsecure, I am re-directed to the home page with "Invalid Form Key. Please refresh the page why because in Magento 2.3 core payment methods are using CsrfAwareActionInterface for each controller."

So now i have implemented same thing in my custom payment method as below

use Magento\Framework\App\CsrfAwareActionInterface;
use Magento\Framework\App\Request\InvalidRequestException;
use Magento\Framework\App\RequestInterface;

class CustomPaymentResponse extends \Magento\Framework\App\Action\Action implements CsrfAwareActionInterface

/** 
 * @inheritDoc
 */
public function createCsrfValidationException(
    RequestInterface $request 
): ?InvalidRequestException {
    return null;
}

/**
 * @inheritDoc
 */
public function validateForCsrf(RequestInterface $request): ?bool
{
    return true;
}

Note : you can get reference from core module. Here is the core file path vendor\magento\module-authorizenet\Controller\Directpost\Payment\BackendResponse.php.

Answer 2

    use Magento\Framework\App\CsrfAwareActionInterface;
    use Magento\Framework\App\Request\InvalidRequestException;
    use Magento\Framework\App\RequestInterface;

    class CustomPaymentResponse extends \Magento\Framework\App\Action\Action implements CsrfAwareActionInterface

    /** 
     * @inheritDoc
     */
    public function createCsrfValidationException(
        RequestInterface $request 
    ): ?InvalidRequestException {
        return null;
    }

    /**
     * @inheritDoc
     */
    public function validateForCsrf(RequestInterface $request): ?bool
    {
        return true;
    }
   /**
     * Dispatch request
     *
     * @return \Magento\Framework\Controller\ResultInterface|ResponseInterface
     * @throws \Magento\Framework\Exception\NotFoundException
     */
   public function execute()
    {
    //your response check
    }

Your response controller should be like this, then only form key issue will fix.

Referrence: https://github.com/magento/magento2/issues/19712