Features and enhancements
- Field sanitization added to prevent possibility of XSS - see security advisory https://security.drupal.org/node/155268.
Important: If you are upgrading from Migrate 2.5 or earlier
Migration developers will need to add the "advanced migration information" permission to their roles to continue seeing all the info in the UI they're used to.
Auto-registration (having classes be registered just based on their class name, with no call to registerMigration or definition in hook_migrate_api()) is no longer supported. Registration of classes defined in hook_migrate_api() is no longer automatic - do a drush migrate-register or use the Register button in the UI to register them.
Migration class constructors should now always accept an $arguments array as the first parameter and pass it to its parent. This version does support legacy migrations which pass a group object, or nothing, but these methods are deprecated.