Steps to reproduce:
1. Login as a user who belongs to a user group which has public pages, and access the public pages of his/her personal site
2. Access one of the pages inherited from the user group and keep the link
3. Login as an administrator and remove the user from the user group
4. Login as the user again and paste the URL in the browser
The user will be able to see the page even if he is no longer a member of the user group.
Alternative steps to reproduce:
1. Login as an administrator of a user group with public pages
2. Go to the public pages of the user group and copy the URL of a page
3. Log out and paste the URL in the browser
Even logged out, it is possible to access the public pages of the user group using its direct URL. In this case, only the administrators of the user group should be able to access the pages.