newsupernova/vendor/magento/module-authorizenet/etc/frontend/events.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
    <event name="checkout_submit_all_after">
        <observer name="directpost_save_order_after_submit" instance="Magento\Authorizenet\Observer\SaveOrderAfterSubmitObserver" />
    </event>
    <event name="checkout_directpost_placeOrder">
        <observer name="directpost_save_order_onepage" instance="Magento\Authorizenet\Observer\AddFieldsToResponseObserver" />
    </event>
</config>