From Authorize.net on March 12, 2019
MD5 Hash End of Life Moved to June 28, 2019
After reviewing feedback concerning the production cutoff date for the MD5 Hash, we are pushing back the production update from March 14, 2019, to June 28, 2019. We will continue to review feedback and consider further date changes as needed over the next month.
On March 14, 2019, Authorize.net will stop supporting MD5 based hash usage. Magento’s implementation of the Authorize.Net Direct Post payment method uses MD5 based hash and this change will result in Magento merchants not being able to process payments using Authorize.Net Direct Post. This issue affects Magento 1 and Magento 2.
If you use Authorize.Net, take the following action to avoid disruption:
For help with applying the patch or changing the MD5 hash to a SHA-512 key, please contact [email protected]