When you upgrade to Carbon Black EDR Server version 6.4.0, the previously used certificate appears in the server certificates table – that is, the certificate called “Legacy”.
Unless you change it, standard validation (certificate pinning) remains in effect. This allows the server and sensors to communicate as before the upgrade.
After the upgrade is complete, you can implement a different certificate management strategy if you choose. Subsequent server upgrades maintain whatever certificates you have in place at the time of the upgrade.