Magento 2: How to find which config causing error “Malformed UTF-8 characters, possibly incorrectly encoded” when trying to serialize checkout config

Question

I'm on Magneto 2.3.4. In vendor/magento/module-checkout/view/frontend/templates/onepage.phtml there's a line like this:

        window.checkoutConfig = <?= /* @noEscape */ $block->getSerializedCheckoutConfig() ?>;

Following the function, it comes down to vendor/magento/module-checkout/Block/Onepage.php::getSerializedCheckoutConfig()

And the serialize function is in vendor/magento/framework/Serialize/Serializer/JsonHexTag.php

I added json_last_error_msg() to the exception message, and basically the error message is now:

Exception #0 (InvalidArgumentException): 
Unable to serialize value. Error:Malformed UTF-8 characters, possibly incorrectly encoded

How to quickly find the checkout configuration value or key that is having malformed UTF-8 characters? Or how to quickly fix this in database?

Answer 1

In the past, I faced the same issue. In my case, a custom payment config encryption caused that issue. Please check the config with encryption, for example: token, password,...