v9.0.1
This dot release addresses a problem with the upgrade process that would cause misconfigured nodes (validators and non validators) to get out of sync.
This problem has been present since day one but has the potential to be more of a problem as validators vote on changing more network wide settings.
Breaking changes
The following settings have been removed from the configuration file: PREFERRED_UPGRADE_DATETIME, DESIRED_BASE_FEE, DESIRED_BASE_RESERVE and DESIRED_MAX_TX_PER_LEDGER.
Read the admin guide for more details on how to configure a validator to vote for network settings changes.
Example "recipe" for a network upgrade can be found at https://github.com/stellar/stellar-core/blob/448efc241cc373c9ca0dc06c72e24bd5ad26238f/docs/software/admin.md#upgrading-network-settings