Authorize.net June 2016 Changes

Authorize.net are changing the URLs used to access their API.
If you do not update your Authorize.net module (osCommerce, WooCommerce and Magento) your module will stop working after 30 June 2016.
You’ve had a year to do this so if you have not yet done it, you need to act immediately.
See http://www.ozeworks.com/2015/07/authorize-net-annouces-api-changes/