Same-day cutoff rules applied server-side at booking creation

Same-day cutoff rules that live only in the slot-filter query are display controls, not booking controls. A direct POST to the booking API bypasses the hidden slots entirely. OWASP A03 (Injection) and CWE-20 (Improper Input Validation) apply whenever a server accepts client-supplied timestamps without verifying them against business rules. Without server-side cutoff enforcement, a customer can schedule a same-day appointment that the host has no time to prepare for, or an automated client can flood the schedule with last-minute bookings.

Add a cutoff constant and validate it against the request timestamp at the booking API handler, not only when generating the list of available slots.

// src/app/api/book/route.ts
const ADVANCE_BOOKING_HOURS = 24

export async function POST(req: Request) {
  const { startTime } = await req.json()
  const requested = new Date(startTime)
  const earliest = new Date(Date.now() + ADVANCE_BOOKING_HOURS * 3_600_000)

  if (requested < earliest) {
    return Response.json(
      {
        error: 'Too soon',
        detail: `Bookings require at least ${ADVANCE_BOOKING_HOURS}h notice`,
      },
      { status: 400 }
    )
  }
  // ... create booking
}

Co-locate this check with duration and buffer validation so all server-side time boundaries are auditable in one place.

• ID: booking-calendar-availability.availability-logic.same-day-cutoff

• Severity: high

• What to look for: Search for advance booking cutoff configuration (e.g., ADVANCE_BOOKING_HOURS = 24, MIN_NOTICE_HOURS, cutoffHours). Count all booking creation API endpoints. For each, verify the server compares the requested time against now + cutoff and rejects requests that violate the rule. Check if this validation is in the API route handler or only in the calendar UI filter. Examine files matching src/app/api/book*/route.ts, src/app/api/appointment*/route.ts, src/lib/*booking*, src/lib/*config*.

• Pass criteria: Count all booking API endpoints. At least 1 advance booking cutoff constant must be defined server-side (e.g., ADVANCE_BOOKING_HOURS). 100% of booking creation endpoints must compare requestedTime against now + cutoffHours and return HTTP 400/409 when violated. Report: "Cutoff hours: [value]. X of Y endpoints enforce server-side."

• Fail criteria: Cutoff is only applied when filtering available slots for display, not when validating a booking request. Or no cutoff constant exists in server-side code.

• Skip (N/A) when: Platform explicitly does not enforce advance booking cutoffs (accepts last-minute bookings by design).

• Detail on fail: Example: "Calendar hides same-day slots, but API does not check. A direct POST with a same-day time succeeds."

• Cross-reference: Check duration-validation — cutoff and duration validations should be co-located in the same API middleware.

• Cross-reference: Check advance-booking-limits — same-day cutoff guards the near end; advance limits guard the far end.

• Cross-reference: Check past-date-protection — client-side past-date guard complements server-side cutoff validation.

• Remediation: Validate cutoff server-side:

  // pages/api/appointments.ts
  const ADVANCE_BOOKING_HOURS = 24
  
  export async function POST(req: Request) {
    const { startTime } = await req.json()
  
    const now = new Date()
    const requestedTime = new Date(startTime)
    const minimumAllowedTime = new Date(
      now.getTime() + ADVANCE_BOOKING_HOURS * 60 * 60 * 1000
    )
  
    if (requestedTime < minimumAllowedTime) {
      return Response.json(
        {
          error: 'Too late to book',
          detail: `Bookings must be made at least ${ADVANCE_BOOKING_HOURS} hours in advance`,
        },
        { status: 400 }
      )
    }
  
    // ... create booking
  }