Improper cooking commonly occurs in both domestic and commercial settings. Common sources include: - Undercooked Meat: Especially poultry, beef, and pork, which require specific internal temperatures to be safe. - Improper Reheating: Leftovers and pre-cooked foods that are not reheated to sufficiently high temperatures. - Cross-Contamination: Using the same utensils or surfaces for raw and cooked foods without proper cleaning in between.