# Risk Scenarios for: checkout flow with Stripe payment integration

## 🔴 CRITICAL (96% confidence)

### Webhook Race Condition

> What if the Stripe webhook arrives before the order database transaction commits?

**Impact:** Payment marked successful in Stripe but order record doesn't exist yet. Webhook processing fails. Customer charged but no order created. Fulfillment never triggered.

**Domain:** payments, concurrency, database

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## 🔴 CRITICAL (93% confidence)

### Payment Succeeds but Inventory Reservation Fails

> What if payment completes successfully but the inventory update throws an exception?

**Impact:** Money charged, but inventory not decremented. Overselling occurs. Items shown as available when sold out. Customer charged for unavailable items.

**Domain:** payments, database

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## 🔴 CRITICAL (90% confidence)

### No Idempotency Key on Payment Intent

> What if the user refreshes or retries during checkout without idempotency protection?

**Impact:** Duplicate Payment Intents created. Customer double-charged. Multiple orders for same cart. Refund overhead.

**Domain:** payments, concurrency

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## 🟠 HIGH (88% confidence)

### Cart Session Expires During Stripe Checkout

> What if the Redis cart session expires while the user is on the Stripe hosted checkout page?

**Impact:** Cart data lost when user returns from Stripe. Cannot complete order. Order total mismatch. Customer must rebuild cart.

**Domain:** payments, infrastructure, concurrency

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## 🟠 HIGH (85% confidence)

### Double-Click Submit Button

> What if the user rapidly clicks "Pay Now" multiple times before the button is disabled?

**Impact:** Multiple payment attempts triggered. Race condition in order creation. Potential duplicate charges before idempotency check.

**Domain:** payments, frontend, concurrency

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## 🟠 HIGH (82% confidence)

### Webhook Signature Verification Skipped

> What if webhook signature validation is missing or improperly implemented?

**Impact:** Forged webhook events accepted. Attacker can mark any order as paid without actually paying. Complete payment fraud vector.

**Domain:** payments, security

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## 🟡 MEDIUM (78% confidence)

### No Timeout on Stripe API Calls

> What if calls to Stripe API hang indefinitely due to network issues?

**Impact:** Checkout process freezes. User sees loading spinner forever. Database connections held. Thread/worker exhaustion.

**Domain:** payments, infrastructure, api

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## 🟡 MEDIUM (75% confidence)

### Order Total Recalculation at Checkout

> What if the order total is recalculated from cart items at payment time instead of using cached total?

**Impact:** Price changes between cart view and payment. User charged different amount than expected. Race condition if prices updated during checkout.

**Domain:** payments, database

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## 🟡 MEDIUM (72% confidence)

### Abandoned Cart Not Cleaned Up

> What if failed/abandoned checkout sessions leave cart records and inventory reservations indefinitely?

**Impact:** Database bloat from stale cart data. "Soft" inventory locks preventing real sales. Memory leak in session store.

**Domain:** database, infrastructure

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**Summary:** Found 9 risk scenarios (3 CRITICAL, 3 HIGH, 3 MEDIUM)

**Generated:** 2026-01-11 by Gremlin v0.1.0
