What are the potential consequences of ignoring or not handling an "INVALID IPN" response?

Ignoring or not handling an "INVALID IPN" response can lead to potential security risks, as it indicates that the IPN message may not be authentic. This could result in unauthorized access to sensitive information or fraudulent transactions being processed. To solve this issue, it is important to verify the authenticity of the IPN message by validating it with the PayPal server. 

// Verify IPN message with PayPal server
$ch = curl_init('https://www.sandbox.paypal.com/cgi-bin/webscr');
curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/x-www-form-urlencoded'));
curl_setopt($ch, CURLOPT_POST, 1);
curl_setopt($ch, CURLOPT_POSTFIELDS, 'cmd=_notify-validate&' . http_build_query($_POST));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

$response = curl_exec($ch);
curl_close($ch);

if ($response == 'VERIFIED') {
    // Process the IPN message
    // Code to handle valid IPN response
} else {
    // Log or handle the INVALID IPN response
    // Code to handle invalid IPN response
}

Keywords

IPN response handling invalid consequences PHP

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