Drupal 8 before 8.2.8 and 8.3 before 8.3.1 allows critical access bypass by authenticated users if the RESTful Web Services (rest) module is enabled and the site allows PATCH requests.

When adding a private file via the editor in Drupal 8.2.x before 8.2.7, the editor will not correctly check access for the file being attached, resulting in an access bypass.

Some administrative paths in Drupal 8.2.x before 8.2.7 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.