Redmine

Hi, responding to an image tag

src="/attachments/download/123/back.png"

Redmine says:

Processing by AttachmentsController#download as */*
  Parameters: {"id"=>"123", "filename"=>"back.png"}
  Current user: Pacient1 (id=26)
  Rendered common/error.html.erb within layouts/base (0.5ms)
  Rendered common/error.html.erb within layouts/base (0.5ms)
Filter chain halted as :read_authorize rendered or redirected

I wonder which view permission should be set?
Regards, Zdravko