What would make posole go bad in one night?

Posole can go bad overnight if it is left out at room temperature for too long, as bacteria can multiply rapidly in the "danger zone" between 40°F and 140°F. If it is not stored in an airtight container or placed in the refrigerator promptly after serving, it can also absorb odors or moisture that promote spoilage. Additionally, ingredients like meat or vegetables can break down and deteriorate faster, leading to off flavors or spoilage. Always refrigerate leftovers within two hours to ensure freshness.