Fixed read private group names

app/controllers/dashboard/todos_controller.rb

@@ -4,6 +4,7 @@ class Dashboard::TodosController < Dashboard::ApplicationController
   include ActionView::Helpers::NumberHelper
 
   before_action :authorize_read_project!, only: :index
+  before_action :authorize_read_group!, only: :index
   before_action :find_todos, only: [:index, :destroy_all]
 
   def index
@@ -60,6 +61,15 @@ class Dashboard::TodosController < Dashboard::ApplicationController
     end
   end
 
+  def authorize_read_group!
+    group_id = params[:group_id]
+
+    if group_id.present?
+      group = Group.find(group_id)
+      render_404 unless can?(current_user, :read_group, group)
+    end
+  end
+
   def find_todos
     @todos ||= TodosFinder.new(current_user, todo_params).execute
   end

changelogs/unreleased/security-private-group.yml

+---
+title: Removed ability to see private group names when the group id is entered in
+  the url.
+merge_request:
+author:
+type: security

spec/controllers/dashboard/todos_controller_spec.rb

@@ -42,6 +42,16 @@ describe Dashboard::TodosController do
       end
     end
 
+    context 'group authorization' do
+      it 'renders 404 when user does not have read access on given group' do
+        unauthorized_group = create(:group, :private)
+
+        get :index, group_id: unauthorized_group.id
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+    end
+
     context 'when using pagination' do
       let(:last_page) { user.todos.page.total_pages }
       let!(:issues) { create_list(:issue, 3, project: project, assignees: [user]) }