Specially crafted requests can be used to access files that exists on the filesystem that is outside an application's root directory, when the Sprockets server is used in production.
All users running an affected release should either upgrade or use one of the work arounds immediately.
The 4.0.0.beta8, 3.7.2 and 2.12.5 releases are available at the normal locations.
In Rails applications, work around this issue, set
config.assets.compile = false and
config.public_file_server.enabled = true in an initializer and precompile the assets.
This work around will not be possible in all hosting environments and upgrading is advised.
To aid users who aren't able to upgrade immediately we have provided patches for the three supported release series. They are in git-am format and consist of a single changeset.