Drupal: CVE-2017-6377: Drupal Core - Multiple Vulnerabilities - SA-CORE-2017-001

Drupal 8.2.7, a maintenance release which contains fixes for security vulnerabilities, is now available for download. Update your existing Drupal 8 sites is strongly recommended. There are no new features nor non-security-related bug fixes in this release. See the 8.2.7 release notes for details on important changes and known issues affecting this release. Read on for details of the security vulnerabilities that were fixed in this release. When adding a private file via a configured text editor (like CKEditor), the editor will not correctly check access for the file being attached, resulting in an access bypass.
Some administrative paths did not include protection for CSRF. This would allow an attacker to disable some blocks on a site. This issue is mitigated by the fact that users would have to know the block ID.
A 3rd party development library including with Drupal 8 development dependencies is vulnerable to remote code execution. This is mitigated by the default .htaccess protection against PHP execution, and the fact that Composer development dependencies aren't normal installed. You might be vulnerable to this if you are running a version of Drupal before 8.2.2. To be sure you aren’t vulnerable, you can remove the /vendor/phpunit directory from the site root of your production deployments.