Authorize.Net is phasing out the MD5 based hash use for transaction response verification in favor of the SHA-512 based hash utilizing a Signature Key.Instead of hashing the transaction key with MD5, it is now required to hash the signature key with SHA-512.
Support for MD5 was stopped March 7 2019 for sandbox environment and will stop on June 28 2019 for production environment.
On February 11, 2019 Authorize.net removed the ability to configure or update MD5 Hash setting in the Merchant Interface. Merchants who had this setting configured have been emailed/contacted.
You can see more information about the change on Authorize.net.
What does it mean for you in Odoo?
We supported both methods up to now, now that support ended for MD5, you just have to update the Authorize.net key you requested in your payment acquirers settings.
Authorize.net end of MD5