Change effective on 05 March 2018
The Heroku Cedar-14 and Heroku-16 stack images have been updated with the most recent versions of installed packages to address a PostgreSQL security advisory.
The new stack images will be rolled out automatically in the next 24 hours. You do not need to redeploy your app or restart your dynos.
See this Dev Center article for an overview of the libraries available on the Cedar-14 and Heroku-16 stack images.