Can't update Defender app on macOS

Microsoft support: 

1. One option is to temporarily switch Tamper Protection to Audit Mode, which will allow the updates to be installed.
2. Alternatively, you can use a Tamper Protection exclusion in combination with the upgrade_helper method. This approach is reliable and does not require changing Tamper Protection to Audit Mode.

You’ll find the steps to initiate the upgrade_helper deployment in the document linked below.

https://github.com/microsoft/mdatp-xplat/tree/master/macos/upgrade_from_2506_helper