Description
Drupal Core is prone to multiple vulnerabilities, including cross-site scripting, security bypass and information disclosure vulnerabilities. Exploiting these issues could allow an attacker to execute arbitrary script code in the browser of an unsuspecting user in the context of the affected site, allowing the attacker to steal cookie-based authentication credentials, to perform otherwise restricted actions and subsequently set comment visibility on nodes or to obtain sensitive information which may help in launching further attacks. Drupal Core versions 8.x ranging from 8.0.0 and up to and including 8.1.9 are vulnerable.
Remediation
Update to Drupal Core version 8.1.10 or latest
References
http://blog.knownsec.com/2016/09/drupal-8-config-download/
https://twitter.com/mdisec/status/778678151920562178