Users with `create` but not `override` privileges can perform local sync in argo-cd

@@ -333,6 +333,15 @@ func (s *Server) Create(ctx context.Context, q *application.ApplicationCreateReq
 		return nil, security.NamespaceNotPermittedError(appNs)
 	}
 
+	// Don't let the app creator set the operation explicitly. Those requests should always go through the Sync API.
+	if a.Operation != nil {
+		log.WithFields(log.Fields{
+			"application":            a.Name,
+			argocommon.SecurityField: argocommon.SecurityLow,
+		}).Warn("User attempted to set operation on application creation. This could have allowed them to bypass branch protection rules by setting manifests directly. Ignoring the set operation.")
+		a.Operation = nil
+	}
+
 	created, err := s.appclientset.ArgoprojV1alpha1().Applications(appNs).Create(ctx, a, metav1.CreateOptions{})
 	if err == nil {
 		s.logAppEvent(created, ctx, argo.EventReasonResourceCreated, "created application")

@@ -1439,6 +1439,27 @@ func TestCreateAppWithDestName(t *testing.T) {
 	assert.Equal(t, app.Spec.Destination.Server, "https://cluster-api.example.com")
 }
 
+// TestCreateAppWithOperation tests that an application created with an operation is created with the operation removed.
+// Avoids regressions of https://github.com/argoproj/argo-cd/security/advisories/GHSA-g623-jcgg-mhmm
+func TestCreateAppWithOperation(t *testing.T) {
+	appServer := newTestAppServer(t)
+	testApp := newTestAppWithDestName()
+	testApp.Operation = &appsv1.Operation{
+		Sync: &appsv1.SyncOperation{
+			Manifests: []string{
+				"test",
+			},
+		},
+	}
+	createReq := application.ApplicationCreateRequest{
+		Application: testApp,
+	}
+	app, err := appServer.Create(context.Background(), &createReq)
+	require.NoError(t, err)
+	require.NotNil(t, app)
+	assert.Nil(t, app.Operation)
+}
+
 func TestUpdateApp(t *testing.T) {
 	testApp := newTestApp()
 	appServer := newTestAppServer(t, testApp)