[CVE-2017-6377] Editor module incorrectly checked access to inline private files

When added a private file via a configured text editor (like CKEditor), the editor would not correctly check access for the file being attached, resulted in an access bypass.

Part of security patch SA-CORE-2017-001

This vulnerability affects the following application versions:

• Drupal 8.2.2
• Drupal 8.2.3
• Drupal 8.2.4
• Drupal 8.2.5
• Drupal 8.2.6