edx-platform/lms/templates/shoppingcart/cybersource_form.html

<%! from django.utils.translation import ugettext as _ %>
    <form action="${action}" method="post">
        % for pk, pv in params.iteritems():
            <input type="hidden" name="${pk}" value="${pv}" />
        % endfor

        <button type="submit">${_('Payment')}<span class="icon fa fa-caret-right" aria-hidden="true"></span></button>
    </form>