J3.x:Unable To Edit Article 3.4.7
From Joomla! Documentation
Joomla! 3.4.7 changed how session management was done in the CMS (see the patch notes for more information). However a side affect was that people were unable to edit articles/modules etc.
You are not allowed to access this link directly [itemid]
What is the cause
Joomla changed the session storage mechanism. Some parts of your session data were migrated to ensure the update process was successful. Only the data necessary to finish the update was migrated and some data related to user permissions wasn't migrated successfully.
How to fix
Logging out and back in again will fix this issue.