Steps to reproduce the issue

http://cdl.joomlademos.co.uk
login with : mcr_brighton / mcr_brighton

Expected result

http://cdl.joomlademos.co.uk/index.php?option=com_content&view=featured&Itemid=1207

Actual result

http://cdl.joomlademos.co.uk/index.php?option=com_content&view=featured&Itemid=1207

System information (as much as possible)

Joomla 3.6.3
Database Version 5.6.30-log
Database Collation utf8_unicode_ci
Database Connection Collation utf8mb4_general_ci
PHP Version 5.6.24

Additional comments

I am using a plugin that redirects users to a specific page based on user/user groups.
The plugin is using this bit to redirect : if($itemid) $app->redirect(JRoute::_($menuitem->link.'&Itemid='.$itemid));

The problem is that for some reason the '&' is replaced with '&' in the output...