* **Raft Protocol Defaults to 3:** The [`-raft-protocol`](https://www.consul.io/docs/agent/options.html#_raft_protocol) default has been changed from 2 to 3, enabling all Autopilot features by default. Version 3 requires Consul running 0.8.0 or newer on all servers in order to work, so if you are upgrading with older servers in a cluster then you will need to set this back to 2 in order to upgrade. See [Raft Protocol Version Compatibility](https://www.consul.io/docs/upgrade-specific.html#raft-protocol-version-compatibility) for more details. Also the format of `peers.json` used for outage recovery is different when running with the lastest Raft protocol. See [Manual Recovery Using peers.json](https://www.consul.io/docs/guides/outage.html#manual-recovery-using-peers-json) for a description of the required format. [GH-3477]
* **HTTP Verb Enforcement:** Many endpoints in the HTTP API that previously took any HTTP verb now check for specific HTTP verbs and enforce them. This may break clients relying on the old behavior. The table below has the endpoints that were updated. [GH-3405]