I had a user report that after entering a coupon, with a total owed of $0.78 that Zen-Cart allowed her to complete the order without entering in payment details.

I tried the same thing, with very similar results. The coupon covered the item costs, but not the shipping, which showed an amount due of $7.05. The cart let me complete the order without entering in payment details! If I create an order without a coupon, or using a coupon that only partially covers the amount, it requires payment.

I am using Authorize.net AIM as my only payment method on ZC 1.3.7 with no customizations. I am also looking at upgrading to 1.3.8.

Any ideas what's going on?