wp-e-commerce/WP-e-Commerce — pull request #1071 by jbeales (2014-04-10 17:10:34+00:00)
Title: Disable checkout submit after submission.

Add Javascript to disable and submit buttons, input[type=“submit”], in
the checkout form when the form is submitted. This way anyone with
Javascript enabled can’t double-submit a purchase.

This is at least a partial fix for #1038.