According to the Hadith, food should be covered during the night.

Answer

Food left uncovered throughout the night remains halaal. However, there is a possibility of shaitaan having interfered with the open food. It is therefore best to feed it to the animals. But it remains permissible. However, caution demands that one abstains. It is mentioned in the Hadith that on a particular night during the year, a calamity descends from the skies and settles on uncovered foodstuff. The effect is disease and other misfortunes. The specific night is not mentioned. For example, if one is told that someone may have added some poison to the food during the night time, we are sure no one will eat the food.