Ecommerce security review before Black Friday: what to check before traffic, bots and checkout hit production

An ecommerce security review is a structured assessment of risks that can stop sales, expose customer data or increase incident cost. In practice, it should combine architecture review, application testing, API testing, infrastructure configuration review, log analysis, selected load tests and a decision workshop with the business.

For headless or B2B commerce, the boundaries between the Next.js storefront, NestJS backend, commerce core, MedusaJS, PostgreSQL, payments, ERP/PIM/WMS and marketing automation matter. Incidents rarely stay in one layer. Missing API rate limits can become email queue overload, SMS cost spikes, delayed inventory sync and a wrong delivery promise in checkout.

OWASP API Security Top 10 2023 lists Broken Object Level Authorization as the first API risk: endpoints that receive object identifiers must verify that the logged-in user can perform the action on the specific record. In commerce this is concrete. It touches carts, orders, invoices, shipping addresses, wishlists, B2B accounts, credit limits and admin panels.

The second area is Unrestricted Resource Consumption. APIs consume CPU, memory, bandwidth, email, SMS, paid validations, webhooks and provider limits. During peak season an attacker does not need to steal data to hurt the business. Burning a queue, SMS budget or payment-provider limit can be enough.

The third area is Unrestricted Access to Sensitive Business Flows. A bot does not have to break passwords to cause damage: it can reserve stock, generate carts, test coupons, create accounts, scrape prices or overload search. The review should test not only technical vulnerabilities, but also automated abuse of flows that make business sense only at human speed.

Akamai State of the Internet 2025 reports a 33% year-over-year increase in global web attacks and rising OWASP API Top 10, bot and AI-assisted automation risk. That matters for ecommerce because peak traffic already looks abnormal. Poorly tuned defense can let bad traffic through or block real buyers.

A pre-peak review should therefore ask more than "do we have a WAF?". It should check per-endpoint rules, limits per customer/account/IP/device, integration exceptions, bot challenge flows, caching, origin shielding, queues, graceful degradation and the manual policy-tightening plan for when the campaign is live.

The most practical tests do not simulate the whole internet. They simulate specific abuse scenarios: listing scraping, credential stuffing, mass carts, registration spam, coupon brute force, search bursts, many parallel payment callbacks and a sudden request spike from one country or ASN. Every scenario should have an expected log signal and an operational decision.

The PCI Security Standards Council maintains PCI DSS as the payment-card data security standard; in practice, ecommerce teams must understand where the payment provider responsibility ends and the store responsibility begins. Redirecting payment to a provider does not remove responsibility for secure checkout configuration, webhooks, scripts, logs and admin access.

Before peak, check idempotency keys, replay protection, payment-status validation, webhook retries, order-submit race conditions, partial failure handling, log masking, alerts for increased declined payments and manual reconciliation procedure. In B2B, add credit limits, pay-by-invoice, approval flow and rules for blocking overdue customers.

This is where security review meets product architecture. If an order can be created without confirmed payment, payment can be captured without an order, or stock can be reserved without expiration, the risk belongs to finance and operations, not only security.

In ecommerce, major leaks often do not start with a dramatic breach. They start with overly broad privileges, a wrong tenant_id filter, full payload logging, a debug endpoint, an unprotected backup or an admin panel that reveals too much.

If the system supports marketplaces, B2B buyers, multiple brands, wholesalers or organizational roles, the review should test PostgreSQL Row-Level Security or an equivalent data-isolation mechanism. RLS does not replace application controls, but it creates another barrier when API code makes a mistake. Test it negatively: a user from company A must not see company B carts, invoices, credit limits or history.

Data also means retention and logs. Before the campaign, decide which data is needed to diagnose incidents and which must never be logged. The team should have queries ready for anomaly detection without exporting sensitive data into tools that should not store it.

Without observability, a security review ends as a presentation, not operational readiness. The team needs four signal groups: availability, conversion, abuse and data access. In practice, this means dashboards for checkout latency, error rate, payment failures, queue depth, bot challenges, blocked requests, failed logins, admin actions, webhook retries and unusual data queries.

Incident response should be short and concrete. Who may tighten WAF rules? Who approves disabling a discount code? Who informs customer service when payment errors rise? Who decides rollback? Who has access to the payment provider, DNS, CDN and repository? If answers are invented during Black Friday, it is too late.

The simplest readiness test is a tabletop exercise. For 60-90 minutes the team walks through a scenario: bots generate carts, checkout latency rises, the payment provider returns errors and marketing asks whether to stop the campaign. That exercise reveals more truth than ten status meetings.

At GMI, we treat security through product and operations, not only a vulnerability list. For headless stores, B2B commerce and mobile commerce apps, we combine architecture review, backend/API, Next.js, MedusaJS, NestJS, PostgreSQL, queues, payments, ERP/PIM/WMS, mobile release and observability.

First, we run a DDT security scope: revenue path, sensitive data, integrations, roles, permissions, failure points and vendor dependencies. Then we create a prioritized backlog: must fix before peak, should fix, monitor, accept. For agreed scope, we can propose fixed-price remediation, with source code and documentation owned by the client.

This approach is especially useful when the store has custom checkout, MedusaJS or another headless core, NestJS backend, PostgreSQL, ERP/PIM/WMS integrations or a React Native/Expo app. In these systems, security is part of sales architecture, not a plugin added at the end.