Do not show moved issue ids for user not authorized

Do not show moved issue id for users that cannot read issue

app/serializers/issue_entity.rb

@@ -16,9 +16,14 @@ class IssueEntity < IssuableEntity
   expose :discussion_locked
   expose :assignees, using: API::Entities::UserBasic
   expose :due_date
-  expose :moved_to_id
   expose :project_id
 
+  expose :moved_to_id do |issue|
+    if issue.moved_to_id.present? && can?(request.current_user, :read_issue, issue.moved_to)
+      issue.moved_to_id
+    end
+  end
+
   expose :web_url do |issue|
     project_issue_path(issue.project, issue)
   end

changelogs/unreleased/security-hide_moved_issue_id.yml

+---
+title: Do not show moved issue id for users that cannot read issue
+merge_request:
+author:
+type: security

spec/serializers/issue_entity_spec.rb

@@ -17,4 +17,37 @@ describe IssueEntity do
   it 'has time estimation attributes' do
     expect(subject).to include(:time_estimate, :total_time_spent, :human_time_estimate, :human_total_time_spent)
   end
+
+  context 'when issue got moved' do
+    let(:public_project) { create(:project, :public) }
+    let(:member) { create(:user) }
+    let(:non_member) { create(:user) }
+    let(:issue) { create(:issue, project: public_project) }
+
+    before do
+      project.add_developer(member)
+      public_project.add_developer(member)
+      Issues::MoveService.new(public_project, member).execute(issue, project)
+    end
+
+    context 'when user cannot read target project' do
+      it 'does not return moved_to_id' do
+        request = double('request', current_user: non_member)
+
+        response = described_class.new(issue, request: request).as_json
+
+        expect(response[:moved_to_id]).to be_nil
+      end
+    end
+
+    context 'when user can read target project' do
+      it 'returns moved moved_to_id' do
+        request = double('request', current_user: member)
+
+        response = described_class.new(issue, request: request).as_json
+
+        expect(response[:moved_to_id]).to eq(issue.moved_to_id)
+      end
+    end
+  end
 end