Stripe and PayPal: Issue warning on payments for paid orders

src/pretix/plugins/stripe/signals.py

@@ -84,6 +84,8 @@ def pretixcontrol_action_display(sender, action, request, **kwargs):
         template = get_template('pretixplugins/stripe/action_refund.html')
     elif action.action_type == 'pretix.plugins.stripe.overpaid':
         template = get_template('pretixplugins/stripe/action_overpaid.html')
+    elif action.action_type == 'pretix.plugins.stripe.double':
+        template = get_template('pretixplugins/stripe/action_double.html')
 
     ctx = {'data': data, 'event': sender, 'action': action}
     return template.render(ctx, request)

src/pretix/plugins/stripe/templates/pretixplugins/stripe/action_double.html

@@ -0,0 +1,9 @@
+{% load i18n %}
+
+<p>
+    {% url "control:event.order" organizer=event.organizer.slug event=event.slug code=data.order as ourl %}
+    {% blocktrans trimmed with charge=data.charge stripe_href="href='https://dashboard.stripe.com/payments/"|add:data.charge|add:"' target='_blank'"|safe order="<a href='"|add:ourl|add:"'>"|add:data.order|add:"</a>"|safe %}
+        The Stripe transaction <a {{ stripe_href }}>{{ charge }}</a> has succeeded, but the order {{ order }} has
+        already been paid by other means. Please double-check and refund the money via Stripe's interface.
+    {% endblocktrans %}
+</p>

src/pretix/plugins/stripe/views.py

@@ -199,6 +199,15 @@ def charge_webhook(event, event_json, charge_id):
                 'charge': charge_id
             })
         )
+    elif order.status == Order.STATUS_PAID and not order.payment_provider.startswith('stripe') and charge['status'] == 'succeeded' and not is_refund:
+        RequiredAction.objects.create(
+            event=event,
+            action_type='pretix.plugins.stripe.double',
+            data=json.dumps({
+                'order': order.code,
+                'charge': charge.id
+            })
+        )
     elif order.status in (Order.STATUS_PENDING, Order.STATUS_EXPIRED) and charge['status'] == 'succeeded' and not is_refund:
         try:
             mark_order_paid(order, user=None)