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Security Best Practices for Payment Gateways

A deep dive into CSRF protection, input sanitization, and securing webhooks.

Security is the foundation of any payment system. A single vulnerability can lead to financial loss and a complete loss of trust. In this article, we discuss the critical security layers every payment gateway integration must have.

1. Input Sanitization & Validation

Never trust user input. At Lumen Pay, we enforce strict type checking and sanitization on all incoming API requests. We use a "whitelist" approach, where only expected characters and formats are allowed. For example, a currency field must match a predefined ISO 4217 list.

2. CSRF Protection

Cross-Site Request Forgery (CSRF) attacks occur when a malicious site tricks a user into performing an action on another site where they are authenticated. We mitigate this by requiring a unique, unpredictable token for every state-changing request (POST, PUT, DELETE).

3. Securing Webhooks

Webhooks are a common attack vector. If an attacker discovers your webhook endpoint, they could send fake payment success notifications. To prevent this, Lumen Pay signs every webhook event using an HMAC-SHA256 signature.

// Verifying a Webhook Signature
$payload = file_get_contents('php://input');
$signature = $_SERVER['HTTP_X_LUMEN_SIGNATURE'];
$secret = 'your_webhook_secret';

$expected = hash_hmac('sha256', $payload, $secret);

if (hash_equals($expected, $signature)) {
    // Request is authentic
}

4. Rate Limiting

To prevent brute-force attacks on card testing, we implement strict rate limiting. IPs or API keys that generate excessive failed transactions are temporarily blocked.

Conclusion

Security is not a one-time feature but a continuous process. By implementing these best practices, you ensure that your integration with Lumen Pay remains robust and secure against evolving threats.

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