[willlll]

Heroku runs whatever version you say in your Gemfile. You must update your apps yourself; There is nothing Heroku can do to update your app for you.

[thewillcole]

But am I protected if I'm currently using a fixed version of Rails? (3.2.11, 3.1.10, 3.0.19, or 2.3.15)

[willlll]

yes