Hi,

I found an upload issue for anonymous users, here is the details to re-produce the issue:

1. Anonymous role: keep default setting, i.e. NO "Add Issue" permission
2. Reporter role: keep default setting, i.e. HAS "Add Issue" permission
3. Create a project
4. Add Anonymous users to members list of the project, as Reporter
5. Now Anonymous user can Add Issue and save
6. However, while uploading file, authentication box will popup
7. If I change Anonymous role to check "Add Issue", file upload is ok

The expected result is:
When Anonymous users added to project as reporter, they can add issue and can upload files,
without the needs to change Anonymous role, which will affect all public projects

Environment:
  Redmine version                3.4.7.stable
  Ruby version                   2.4.4-p296 (2018-03-28) [x86_64-linux]
  Rails version                  4.2.11
  Environment                    production
  Database adapter               Mysql2
SCM:
  Subversion                     1.7.14
  Git                            1.8.3.1
  Filesystem                     
Redmine plugins:
  clipboard_image_paste          1.13
  custom_users_as_assignees      0.0.3
  customfield_checkbox_utility   0.0.2
  redmine_checklists             3.1.11
  redmine_email_inline_images    1.0.0
  redmine_helpdesk               0.0.15
  redmine_knowledgebase          3.3.1
  redmine_lightbox2              0.4.3
  redmine_logs                   0.1.1
  redmine_more_code              1.0.0
  redmine_preview_inline         1.0.2

Regards
Wicky