Could not validate nonce O_o

Hello,

Since updating WooCommerce to version 5.6.0 the other day, PayPal integration has broken down. This is true for both the standard PayPal payment method and the more recent PayPal Payments plugin which supports Pay Later and PayPal’s credit card processing.

When clicking on the PayPal yellow button, the PayPal login window opens momentarily but quickly closes and an error message appear above the checkout: “Something went wrong. Please try again or choose another payment source.”

I believe I found the culprit in the logs:

2021-08-20T13:43:56+00:00 CRITICAL Uncaught WooCommerce\PayPalCommerce\Button\Exception\RuntimeException: Could not validate nonce. in /home/patchc5/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Endpoint/class-requestdata.php:50
Stack trace:
#0 /home/patchc5/public_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 /home/patchc5/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/class-buttonmodule.php(111): WooCommerce\PayPalCommerce\Button\Endpoint\DataClientIdEndpoint->handle_request()
#2 /home/patchc5/public_html/wp-includes/class-wp-hook.php(303): WooCommerce\PayPalCommerce\Button\ButtonModule::WooCommerce\PayPalCommerce\Button\{closure}('')
#3 /home/patchc5/public_html/wp-includes/class-wp-hook.php(327): WP_Hook->apply_filters('', Array)
#4 /home/patchc5/public_html/wp-includes/plugin.php(470): WP_Hook->do_act in /home/patchc5/public_html/wp-content/plugins/woocommerce-paypal-payments/modules/ppcp-button/src/Endpoint/class-requestdata.php on line 50

Some kind of a nonce nonsense.

The browser’s Console reports this error:

[Error] Failed to load resource: the server responded with a status of 500 () (www.patchcad.com, line 0) // (https://www.patchcad.com/?wc-ajax=ppc-create-order)

[Error] create_order_error – {err: "The string did not match the expected pattern.???h…nt=capture&enable-funding=venmo,paylater:2:141569", timestamp: "1629531497240", referer: "www.paypal.com", …}

[Error] click_initiate_payment_reject – {err: "The string did not match the expected pattern.???h…nt=capture&enable-funding=venmo,paylater:2:141569", timestamp: "1629531497246", referer: "www.paypal.com", …}

[Error] unhandled_error – {err: "The string did not match the expected pattern.???h…nt=capture&enable-funding=venmo,paylater:2:141569", timestamp: "1629531497261", referer: "www.paypal.com", …}

[Error] Error: The string did not match the expected pattern.
	(anonymous function) (buttons:1317:19223)

Is anybody else experiencing this?

Thank you!