There has been a security release for CiviCRM. Upgrades are available for:

• CiviCRM v5.40.2: https://civicrm.org/download (release notes)
• CiviCRM v5.39.2 ESR: https://civicrm.org/esr (https://lab.civicrm.org/esr/core/-/releases)

These upgrades address security issues in a third-party package:

• CIVI-SA-2021-09: CKEditor (Multiple vulnerabilities)

Please note that this particular advisory has multiple solutions.  Upgrading CiviCRM is the best solution, but if you cannot do that in a timely way, then review the advisory for alternatives and short-term mitigations.