Describe the bug

Merchants are experiencing this error:

021-07-30T21:28:37+00:00 CRITICAL Uncaught WooCommerce\PayPalCommerce\Button\Exception\RuntimeException: Could not validate nonce. in /var/www/html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Endpoint/class-requestdata.php:50
Stack trace:
#0 /var/www/html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Endpoint/class-dataclientidendpoint.php(69): WooCommerce\PayPalCommerce\Button\Endpoint\RequestData->read_request('ppc-data-client...')
#1 /var/www/html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/class-buttonmodule.php(111): WooCommerce\PayPalCommerce\Button\Endpoint\DataClientIdEndpoint->handle_request()
#2 /var/www/html/wp-includes/class-wp-hook.php(303): WooCommerce\PayPalCommerce\Button\ButtonModule::WooCommerce\PayPalCommerce\Button\{closure}('')
#3 /var/www/html/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters('', Array)
#4 /var/www/html/wp-includes/plugin.php(470): WP_Hook->do_action(Array)
#5 /var/www/html/wp-content/plugins/woocommerce/includes/clas in /var/www/html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Endpoint/class-requestdata.php on line 50

To reproduce

• Visit WooCommerce > Settings > Accounts & Privacy
• Disable the guest user checkout option (first checkbox)
  
• Enable option to register account in checkout
• Enable either of the checkboxes to auto-generate account name/password (both also cause the behavior)
• Visit checkout as logged out user and create an order
• A user account will be registered automatically (depending on the settings with auto-generated name or password)
• Payment popup window will result in a loop until the user manually refreshed the site
• After the site refresh, the user is logged into his newly created account and can complete the payment

Also there is another problem which is present even when the guest checkout is enabled and the “Create account” checkbox is checked.

Sometimes instead of finishing the order the checkout page is reloaded, resulting in bad UX + it is not possible to finish ordering because of duplicated PayPal order.

It seems random, sometimes it finishes fine, sometimes it reloads the checkout page. I think it is reproduced more often when DevTools is opened. So maybe there is a bug related to caching of HTTP requests and/or a race condition.

Possible cause

We use createaccount checkbox to determine whether the user needs to created

Environment

• WordPress Version: 5.8, 5.3
• WooCommerce Version: 5.6, 4.7
• WooCommerce PayPal Payments Plugin Version: 1.5.1