It includes several security and many bug-fixes. See the ruby-2.4.2 release post and the the RubyInstaller CHANGELOG for more details.

All binaries are available in the Download section!

A previous RubyInstaller-2.4.x installation can be updated by installing the new version into the same directory. Installed gems are not overwritten and will work with the new version without re-installation. If the previous RubyInstaller version is 2.4.1-1, it’s recommended to run ridk install once again, as offered on the last install page.