Symfony 6.0.0, the latest version just got released 18 hours ago and is reported to be stable. Here are some insights from someone from the Drupal Inner Circle.
The latest Drupal newsletter reported quite a few security advisory updates. These security updates are for the Core and are moderately critical level.
Drupal Vendor library security release came into effect on August 8th according to PSA . The Core update addresses the CKEditor cross-site scripting issue.