Steps to reproduce:
1. Login as "test" user.
2. Add Wiki portlet to the liferay's Home Page.
3. Upload an attachment-1 to Wiki by default.
4. Admin > content > wiki > click main wiki's action button.
7. Check Add Attachment permission of Guest Role.
8. Login as Guest Role.
9. View wiki details and try to download the attachment-1.
10. Try to add attachment-2.
The Guest role could view wiki details and download the attachment-1.
The Guest role could upload attachment with "Add Attachment" permission.