There will be a security release of Drupal 8.3.x and 8.2.x on April 19th 2017 between
17:00 - 18:00 UTC that will fix a critical vulnerability. While we don't normally provide security releases for unsupported minor releases, given the potential severity, we will provide an 8.2.x release that includes the fix for sites which have not had a chance to update to 8.3.0. The Drupal Security Team urges you to reserve time for core updates at that time because exploits are expected to be developed within hours or days. Security release announcements will appear at the standard announcement locations.
This vulnerability does not affect all Drupal 8 sites; it only affects sites with certain configurations. It requires authenticated user access to exploit. The security release announcement on April 19th 2017 will make it clear which configurations are affected. If this vulnerability affects your site, you will need to update. Please set aside time on Wednesday to look into this update.
Neither the Security Team, nor Security Team members, nor any Drupal-related company are able to release any more information about this vulnerability until the announcement is made in accordance with our security policies and responsible disclosure best practices.
We provide pre-release warnings when we believe the security risk is high and the steps to exploit are scriptable.Drupal 7 core is not affected by this issue. Contact and More Information
The Drupal security team can be reached at security at Drupal.org or via the contact form at https://www.drupal.org/contact.
Follow the Drupal Security Team on Twitter at https://twitter.com/drupalsecurity.