Changelog for 2.123

Legend:

security fix
major bug fix
bug fix
major enhancement
enhancement

Community feedback:

no major issues
notable issues
required rollback

What's new in 2.123 (2018-05-21)

A Maven issue prevented 2.123 from being properly released. Use 2.124 instead.

Upgrade Winstone from 4.2 to 4.3, adding an option to enable JMX when running Jenkins using java -jar jenkins.war. (pull 3422, full changelog, JMX Documentation for Jetty, full list of options)
Improve Jenkins root URL validation. (issue 51158)
Prevent unhandled ClassCastException when loading fingerprints from corrupted files. (issue 51179)