Drupal 8.3.4 and Drupal 7.56 are maintenance releases which contain fixes for security vulnerabilities.
Download Drupal 8.3.4
Download Drupal 7.56
Updating your existing Drupal 8 and 7 sites is strongly recommended (see instructions for Drupal 8 and for Drupal 7). This release fixes security issues only; there are no new features nor non-security-related bug fixes in this release. See the 8.3.4 release notes and the 7.56 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.
Advisory ID: DRUPAL-SA-CORE-2017-003
Project: Drupal core
Version: 7.x, 8.x