Update Rails to Latest

Edit your Gemfile updating the line:

gem 'rails', '3.2.12'

to reflect the proper version. Update rails to latest:

bundle update rails

or install a specific version:

gem install rails --version=3.2.12
gem install rails --version=3.1.11
gem install rails --version=3.0.20
gem install rails --version=2.3.17

If you are using Passenger, restart apache / nginx. Default rails installs let you see version information at this URL:

http://example.com/rails/info/properties