Checking the signature of webhooks
In the merchant settings you will find Secret key for verification. It is used to verify the authenticity of incoming webhooks.
PHP validation example:
php
<?php
$secretKeyStored = 'your secret key';
$signFromRequest = $_SERVER['HTTP_X_SIGN'];
$json = file_get_contents('php://input');
$signCalculated = hash('sha256', $json . $secretKeyStored);
var_dump(hash_equals($signFromRequest, $signCalculated));