Maintenance and security release of the Drupal 8 series.
This release fixes critical security vulnerabilities. Sites are urged to upgrade immediately after reading the notes below and the security announcement:
Download library over https
Replace serialize/unserialze with json_encode/json_decode
Issue #2933501 by jurgenhaas, rashid_786: coding standard issue - short array ( [] ) should be used
Add recommended modules
Issue #2280565 by jurgenhaas: Store monitoring results and add a requirements record