paypal return URL $fname bug fix

Where should I submit a bug report?

evr_content.php:
Down in the “Set payment value for return payments” the return and cancel return URL add_fields for paypal need the variable $fname to be changed to $attendee->fname, otherwise if you cancel out of paying by paypal from the Event Payments page you get an error (the fname in the URL is blank as $fname is not filled anywhere).

https://www.ads-software.com/plugins/event-registration/