Update to Rails 4.2.11
Rails 4.2.11 contains a security fix for Active Job (Fix CVE-2018-16476.) see: https://github.com/rails/rails/blob/474b7392c69852e8932260ea370cd63cf1e4fcaa/activejob/CHANGELOG.md
Changelog: https://github.com/rails/rails/blob/v4.2.11/guides/CHANGELOG.md