Where payment gateways break
The complex relationships between processors, issuers, acquirers, and merchants create countless edge cases. We focus on the logical flaws that automated scanners miss entirely.
Webhook spoofing & bypass
If an attacker can forge a "payment successful" webhook to a merchant, they get goods for free. We test signature validation, replay protections, and payload tampering.
Merchant account isolation
Testing for BOLA/IDOR vulnerabilities that would allow a malicious merchant to view another merchant's transactions, modify webhooks, or alter payout accounts.
Settlement manipulation
Attacking the logic controlling how and when funds are settled. We test for negative amount injection, currency conversion rounding exploits, and delayed-capture bypasses.
Checkout manipulation
Testing the customer-facing payment pages for parameter tampering, price modification, and bypasses of 3D-Secure or OTP verification paths.
Webhook signature replay attack
The gateway correctly signed webhooks to merchants, but lacked replay protection. An attacker could capture a single $1 successful webhook payload and replay it 100 times to the merchant's endpoint, resulting in $100 of credited value. Fix priority: immediate.
PCI DSS & Security Assurance
While compliance checks are necessary, they don't catch business logic flaws. Our reviews dig into how a determined attacker would exploit the bespoke features of your transaction engine, providing real security beyond the baseline PCI requirements.
Ensure your gateway APIs are bulletproof.
Get a Quick Security CheckRelated services and resources
Payment gateway testing draws heavily on API security testing (webhook and merchant endpoint authorization) and penetration testing (checkout flow exploitation). If you also handle customer authentication directly, see authentication security reviews. Related industry testing: mobile money and lending platforms.
Frequently asked questions
Does PCI DSS compliance mean our payment gateway is secure?
PCI DSS sets a baseline for cardholder data protection, but it doesn't cover business logic flaws — the most exploited vulnerabilities in payment gateways. Webhook replay attacks, merchant account isolation failures, and settlement manipulation are all outside the scope of a standard PCI assessment. You need dedicated penetration testing alongside compliance.
How do you test webhook security without affecting live merchants?
We test on staging or sandbox environments that mirror your production webhook infrastructure. For webhook-specific tests, we use controlled payloads that validate signature verification, replay protection, and payload tampering without triggering real merchant integrations.
What's the most common vulnerability you find in Nigerian payment gateways?
Merchant account isolation failures (BOLA/IDOR). We regularly find that one merchant can view another merchant's transaction data, modify webhook URLs, or alter payout bank accounts by manipulating API parameters. This stems from insufficient object-level authorization checks.
Can attackers manipulate checkout amounts on our payment page?
If your checkout flow passes amount or currency parameters from the client side without server-side validation against the original order, yes. We specifically test for price manipulation, currency switching, and 3D-Secure bypass paths in every payment gateway engagement.