What potential security risks should be considered when implementing a CAPTCHA check in a PHP form?

One potential security risk when implementing a CAPTCHA check in a PHP form is the possibility of automated bots bypassing the CAPTCHA and submitting the form. To mitigate this risk, it is important to use a reliable and secure CAPTCHA service that is difficult for bots to solve. 

// Example of implementing Google reCAPTCHA in a PHP form
// Ensure you have registered your site and obtained the necessary keys from Google

$secretKey = "YOUR_SECRET_KEY_HERE";
$responseKey = $_POST['g-recaptcha-response'];
$userIP = $_SERVER['REMOTE_ADDR'];

$verifyURL = "https://www.google.com/recaptcha/api/siteverify?secret=$secretKey&response=$responseKey&remoteip=$userIP";
$response = file_get_contents($verifyURL);
$responseKeys = json_decode($response, true);

if(intval($responseKeys["success"]) !== 1) {
    // CAPTCHA verification failed, handle accordingly
    echo "CAPTCHA verification failed";
} else {
    // CAPTCHA verification successful, proceed with form submission
    // Process form data here
}

Keywords

CAPTCHA PHP form security risks implementation validation

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