When authenticated users are trying to add a link or a picture by using the link button in the html editor available in forums an error message pops up in another window.

You're not authorized to read the document 'Forums'

I can't find any reference to a document 'Forums', if this is referring to a document type. I went to the permissions section in CMSSiteManager and added read and modify permissions for authenticated users for module forums but this didn't help.

Where should I setup read permissions for document Forums ?

I am using version 5.5.3901

Thanks!