Security for Booking Platforms
Booking platforms manage reservations, availability, and payments with time-sensitive operations. Race conditions, overbooking exploits, and cancellation abuse are the most common security issues.
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Why Security Matters for Booking Platforms
Booking systems have inherent race conditions — multiple users trying to book the same slot simultaneously. AI-generated code rarely handles this correctly, leading to overbooking, double charges, or lost reservations. Payment timing is also critical. Charging before confirmation, not handling cancellations properly, or allowing free bookings through timing exploits all create financial risk.
Security Risks
Double-booking race conditions
highConcurrent booking requests for the same slot both succeeding because availability isn't locked.
Mitigation
Use database-level locking when checking and updating availability. Implement optimistic concurrency with version checks or pessimistic locking with SELECT FOR UPDATE.
Price manipulation on bookings
highClients modifying booking prices, durations, or add-on costs in API requests.
Mitigation
Calculate all prices server-side based on the selected slot, duration, and services. Never accept prices from the client.
Cancellation policy bypass
mediumUsers getting full refunds outside the cancellation window through API manipulation.
Mitigation
Enforce cancellation policies server-side. Check the booking time against the cancellation deadline before processing any refund.
Security Checklist
Check and reserve slots in a single atomic database transaction.
All booking costs calculated from your pricing table, not from client input.
Cancellation policies checked and enforced on the server.
Use Stripe payment holds to verify payment before confirming the booking.
Prevent users from holding multiple tentative bookings simultaneously.
If a slot is full, offer waitlist instead of allowing overbooking.
Real-World Scenario
A developer builds a salon booking app using v0. Two customers try to book the same 2pm slot at the same time. The app checks availability, finds the slot open for both requests, and creates two bookings. Both customers are charged and show up at 2pm expecting service. The salon loses a customer and has to refund one booking.
Frequently Asked Questions
How do I prevent double-booking?
Use database-level locking. In PostgreSQL, use SELECT ... FOR UPDATE within a transaction when checking availability. This locks the row so concurrent requests wait their turn. Alternatively, use a unique constraint on (slot_id, date) to prevent duplicates at the database level.
Should I charge before or after confirming the booking?
Use a payment hold (Stripe's "authorize then capture" flow). Authorize the payment, confirm the booking, then capture the charge. If the booking fails, release the hold. This prevents charging for failed bookings.
How do I handle cancellation refunds securely?
Enforce your cancellation policy server-side. Store the booking creation time and your refund windows in the database. When a cancellation request comes in, compare timestamps to determine the refund amount. Never trust client-submitted refund amounts.
Security for Other Use Cases
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