Items appearing in Download Center before payment!

Hi

At the end of last year I built a small e-commerce site for digital downloads (I think with eCart 4).

Although I did extensive testing at the time, I've just discovered that it's possible to download items from the Download Center before making payment.

Fortunately this hasn't been exploited yet. I know this, as the only items in the orderdetails table are the ones I know about (and which have been paid for).

The error is entirely reproducible, using the following route:
1. Go to products page
2. Add items to basket
3. Add/delete more items if you want
4. Click Checkout (takes you to login page)
5. Register & Login
6. Go to shopping basket
7. Click on Checkout
8. View details of order and customer details
9. Go to 'My account' (which has links to shopping basket and download center)
10. Click on Download Center
11. Download unpaid-for products free :-(

For obvious reasons, I'm not going to say where the site is, so I'd be grateful if you would set up a ticket.

(Although I have purchased the upgrade to eCart5, I haven't updated that website yet.)

Thanks!
Alistair