Link to a page viewable only by admins is visible to guests in the navigation
Permalink2) For a page, i change the permission for viewing that page from "guest" to "administrators".
3) I log out.
4) Now, as guest user, i'm still seeing the link to that page in the navigation. Of course, when i click on it, it opens the login page, because the page viewable only by administators. But shouldn't the navigation link to that page also NOT be visible to guests?
(Concrete5 5.7.4.1)

The problem was that full page caching is on. The autonav block is in a global area, not sure if that matters, but only clearing the cache helped. Actually i wanted to avoid that, because all the cache content for my galleries is now gone too and it will take ages to render all these pages for the first time to have their content in the cache again.
I could swear to have cleared the browser cache several times before...
Thanks, so it's good to know that i do not have to clear the C5 cache completely in order to update the autonav block after permission changes.