"[#33293] Apply Authorised Groups changes through the backend to the logged in user in the frontend without re-login

Joomla! Issue Tracker [#33293](http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=33293&start=0)

This PR is the same as [PR 3126](https://github.com/joomla/joomla-cms/pull/3126) submitted by @itbra It has merely been updated to apply against the current staging branch.