void AppCacheGroup::AddUpdateObserver(UpdateObserver* observer) {
  if (queued_updates_.find(observer) != queued_updates_.end())
    queued_observers_.AddObserver(observer);
  else
    observers_.AddObserver(observer);
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.