MySQL 5.7.19 is available from late July 2017 onwards. Below are the changes in this version, compared to the prior one.

1. During installation or upgrade, a reserved user named ‘mysql.session’@’localhost’ will be created exclusively for internal modules and plugins to access the MySQL Server. This account is locked and hence could not be used by client connections.

2. In C11 and C++11 standards, Atomics is a new language feature that is supported by the OS during runtime. A bug was reported when MySQL binaries got dependency on the Solaris atomics library called libsatomic.so. This dependency would break the build of the ODBC Client Library. To fix this in MySQL 5.7.19, the binary is linked to liabatomic.so and the dependency is eliminated.

3. The innodb_undo_logs option is deprecated and is advised to use innodb_rollback_segments instead. These options define the number of rollback segments used by InnoDB engine. These are the storage area that stores the undo log. The innodb_available_undo_logs is deprecated.

4. The administration utility mysqladmin is added to the Database Container Package Docker, since it is highly needed by InnoDB Clusters.

5. On the security side, the OpenSSL library is updated. The Lightweight Directory Access Protocol (LDAP) is made available for the server to authenticate users.

6. A bug is fixed and now the X Plugin (implements a network protocol for communication between MySQL and Document Store Layer) handles expired SSL certificates.

7. For MySQL replications, a variable named group_replication_transaction_size_limit is added that protects a group against failure during large transactions. Group transaction now supports SQL transaction SAVEPOINT.

Overall, lot of changes that enhance functionality, bug fixes and that related to client utilities, replication and InnoDB are implemented in MySQL 5.7.19.

Reference:
https://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-19.html