WIC Waiver Extension Act of 2020 This bill extends authority through September 30, 2021, for the Department of Agriculture (USDA) to grant certain waivers to participants under the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) during the COVID-19 (i.e., coronavirus disease 2019) public health emergency. Specifically, USDA may grant waivers allowing participants under WIC to get certified or recertified without being physically present at a WIC clinic; defer anthropometric and bloodwork requirements necessary to determine nutritional risk; and grant waivers from administrative requirements for WIC if it determines that the requirement cannot be met by a state due to COVID-19, and the waiver is necessary to provide assistance under WIC.