Incompatible Change: Scheduled events now use the MySQL server time zone to determine their schedules, rather than UTC as in previous releases. Because of this change, scheduled event metadata now includes time zone information, which can be seen in the TIME_ZONE column of the INFORMATION_SCHEMA.EVENTS table and the Time zone column in the output of the SHOW EVENTS statement. These columns have been added in this release, along with a time_zone column in the mysql.event table. Due to these changes, events created in previous versions of MySQL cannot be created, viewed, or used until mysql.event has been upgraded. (Bug#16420)

Incompatible Change: INSERT DELAYED statements are not supported for MERGE tables, but the MERGE storage engine was not rejecting such statements, resulting in table corruption. Applications previously using INSERT DELAYED into MERGE table will break when upgrading to versions with this fix. To avoid the problem, remove DELAYED from such statements. (Bug#26464)