Support of Ruby 2.3 has ended

After the release of Ruby 2.3.7 on March 28, 2018, the support of the Ruby 2.3 series was in the security maintenance phase. Security and bug fixes from more recent Ruby versions will no longer be backported to 2.3. And, if a critical security issue is found, we will release an urgent fix for it.

Source: www.ruby-lang.org