bool PDFiumEngine::HandleEvent(const pp::InputEvent& event) {
  DCHECK(!defer_page_unload_);
  defer_page_unload_ = true;
  bool rv = false;
  switch (event.GetType()) {
    case PP_INPUTEVENT_TYPE_MOUSEDOWN:
      rv = OnMouseDown(pp::MouseInputEvent(event));
      break;
    case PP_INPUTEVENT_TYPE_MOUSEUP:
      rv = OnMouseUp(pp::MouseInputEvent(event));
      break;
    case PP_INPUTEVENT_TYPE_MOUSEMOVE:
      rv = OnMouseMove(pp::MouseInputEvent(event));
      break;
    case PP_INPUTEVENT_TYPE_KEYDOWN:
      rv = OnKeyDown(pp::KeyboardInputEvent(event));
      break;
    case PP_INPUTEVENT_TYPE_KEYUP:
      rv = OnKeyUp(pp::KeyboardInputEvent(event));
      break;
    case PP_INPUTEVENT_TYPE_CHAR:
      rv = OnChar(pp::KeyboardInputEvent(event));
      break;
    case PP_INPUTEVENT_TYPE_TOUCHSTART: {
      KillTouchTimer(next_touch_timer_id_);

      pp::TouchInputEvent touch_event(event);
      if (touch_event.GetTouchCount(PP_TOUCHLIST_TYPE_TARGETTOUCHES) == 1)
        ScheduleTouchTimer(touch_event);
      break;
    }
    case PP_INPUTEVENT_TYPE_TOUCHEND:
      KillTouchTimer(next_touch_timer_id_);
      break;
    case PP_INPUTEVENT_TYPE_TOUCHMOVE:
      KillTouchTimer(next_touch_timer_id_);
    default:
      break;
  }
 
   DCHECK(defer_page_unload_);
   defer_page_unload_ = false;
  for (int page_index : deferred_page_unloads_)
     pages_[page_index]->Unload();
  deferred_page_unloads_.clear();
   return rv;
 }

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.