Pimcore Preview Documents are not restricted to logged in users anymore

Pimcore is an Open Source Data & Experience Management Platform. Any call with the query argument `?pimcore_preview=true` allows to view unpublished sites. In previous versions of Pimcore, session information would propagate to previews, so only a logged in user could open a preview. This no longer applies. Previews are broad open to any user and with just the hint of a restricted link one could gain access to possible confident / unreleased information. This vulnerability is fixed in 11.2.2 and 11.1.6.1.