Active-active Cluster In MySQL
You appear to be missing the distinction between "Percona XtraDB" and "Percona XtraDB Cluster," also known as PXC.  XtraDB is Percona's compatible drop-in replacement rewrite of the InnoDB storage engine, which is included in Percona Server and MariaDB.

Percona XtraDB Cluster and MariaDB Galera Cluster both use XtraDB as their storage engine, but the important difference from standard MySQL replication is that they both use the Galera Replication Provider, which provides true synchronous replication among all the nodes.  You can also use Galera with MySQL.  Oracle may not mention that, since it wasn't their idea.

MySQL's built-in asynchronous replication can be configured for circular replication (and is included in Percona and MariaDB) but it has no mechanism for handling conflicts.  If queries make conflicting changes on different servers, your data will be inconsistent and replication will stop.  Galera resolves this by requiring all nodes to concur on each commit.  It's replication mechanism is fundamentally different than what is built in.

There are no issues with circular replication that are specific to MySQL 5.6 and 5.7 as your question implies.  These issues apply to all versions of MySQL, Percona, and MariaDB when standard replication is used in a circular configuration, if you allow writes to be done to more than one of the masters.

See http://galeracluster.com