TYPO3 Core

When accessing restricted pages (fe_group) as a logged in frontend user (fe_user), and there is simultaneously an existing backend user session, the "preview" notice is always shown in frontend for those restricted pages. As soon as the backend user is logged out, no "preview" message is shown for the same page. There is no "ADMCMD_simUser=123" involved (not using the backend preview function), it happens by just calling the frontend pages directly.

My setup:

+ Start (Shortcut first subpage)
+--- TreeA (fe_group set, extendToSubpages set)
+----- PageA
+----- PageB
+----- PageC
+--- Login

Now accessing any page inside "TreeA" as a logged in frontend user (while simultaneously logged into the backend), will show the "preview" message.