We will be testing removal of MD5 Hash value from API responses on 04/23/2019 between 9:00am to 11:00am PT, during this time the MD5 Hash field will be present but the value will be empty.
For more details, see MD5 Hash End of Life & Signature Key Replacement article - https://support.authorize.net/s/article/MD5-Hash-End-of-Life-Signature-Key-Replacement
