Only return commands_changes used in frontend

When executing quick actions, this limits the `commands_changes`
response to only those used by the frontend

app/controllers/concerns/notes_actions.rb

@@ -48,7 +48,7 @@ module NotesActions
     respond_to do |format|
       format.json do
         json = {
-          commands_changes: @note.commands_changes
+          commands_changes: @note.commands_changes&.slice(:emoji_award, :time_estimate, :spend_time)
         }
 
         if @note.persisted? && return_discussion?

changelogs/unreleased/security-2826-fix-project-serialization-in-quick-actions.yml

@@ -0,0 +1,5 @@
+---
+title: Remove project serialization in quick actions response
+merge_request:
+author:
+type: security

spec/controllers/projects/notes_controller_spec.rb

@@ -413,6 +413,37 @@ describe Projects::NotesController do
         end
       end
     end
+
+    context 'when creating a note with quick actions' do
+      context 'with commands that return changes' do
+        let(:note_text) { "/award :thumbsup:\n/estimate 1d\n/spend 3h" }
+
+        it 'includes changes in commands_changes ' do
+          post :create, params: request_params.merge(note: { note: note_text }, format: :json)
+
+          expect(response).to have_gitlab_http_status(200)
+          expect(json_response['commands_changes']).to include('emoji_award', 'time_estimate', 'spend_time')
+          expect(json_response['commands_changes']).not_to include('target_project', 'title')
+        end
+      end
+
+      context 'with commands that do not return changes' do
+        let(:issue) { create(:issue, project: project) }
+        let(:other_project) { create(:project) }
+        let(:note_text) { "/move #{other_project.full_path}\n/title AAA" }
+
+        before do
+          other_project.add_developer(user)
+        end
+
+        it 'does not include changes in commands_changes' do
+          post :create, params: request_params.merge(note: { note: note_text }, target_type: 'issue', target_id: issue.id, format: :json)
+
+          expect(response).to have_gitlab_http_status(200)
+          expect(json_response['commands_changes']).not_to include('target_project', 'title')
+        end
+      end
+    end
   end
 
   describe 'PUT update' do