major enhancement 
enhancement
major bug fix 
bug fix
major enhancement enhancement
major bug fix bug fix
= I use it on my production site without major issues. 
= I don't recommend it. 
= I tried it but rolled back to a previous version. Jenkins.getInstance() returns null instance.
It was causing failures on Jenkins agents in the case of unexpected API usage by agents.
(issue 34857, regression in 2.4)
jenkins.model.Jenkins.disableExceptionOnNullInstance by
jenkins.model.Jenkins.enableExceptionOnNullInstance to address the
behavior change.
(issue 34857)
jenkins-ui (NPM module) is private, used only internally.
(issue 34629)
AbortExceptions.
(pull 2288)
hudson.model.UpdateCenter.defaultUpdateSiteId system property,
which allows specifying an alternate default Update Site ID.
(issue 34674)
context.xml and web.xml
in addition to setting system properties from the command line.
(issue 34755)
UpdateCenter by a custom implementation.
(issue 34733)
PluginManager by a custom implementation.
(issue 34681)
PeriodicWork if update site certificate is missing.
(issue 34745)
Downloadable items on restart if all update centers are up to date.
(issue 32886)
AbstractProject (e.g. Pipeline) jobs from CLI.
(issue 28071)
NoSuchMethodException in loginLink.jelly
when attempting to start a job using REST API.
(issue 31618)
ToolInstallers to follow HTTP 30x redirects.
(issue 23507)
NullPointerException in the parameter definition job property
if it gets initialized incorrectly.
(issue 34370)
Font Awesome and Google Fonts: Roboto dependencies
to prevent failures in the offline mode.
(issue 34628)
disconnect-node and reload-configuration were extracted from the core to CLI.
(issue 34328 and
issue 31900)
Jenkins.getInstance() to @Nonnull.
(new system property)
(pull 2297)
NullPointerException from BuildTrigger$DescriptorImpl.doCheck when using Build other projects in Promotion process of a CloudBees template, and perhaps other circumstances.
(issue 32525)
FutureImpl.cancel() doesn't cancel the linked job.
(issue 33038)
JENKINS_HOME/*.log to JENKINS_HOME/logs/tasks/*.log and rotate them periodically rather than overwrite every execution.
(issue 33068)
--pluginroot CLI option (also controllable via the hudson.PluginManager.workDir system property / context parameter. Also document the --webroot CLI parameter in java -jar jenkins.war --help
(issue 32765)
plugin-pom repository, starting with version 2.0.
(issue 32493)
IdleOfflineCause class.
(commit 7e05b50)
--webroot argument to extract the war file into %BASE%.
(pull 1951)
enum.jelly form element.
(PR 1926)
ClassCircularityError exception in Ruby Runtime Plugin.
(issue 31019)
online-node command implementation, no functional changes.
(issue 31776)
hudson.Plugin.
(PR 1940)
Computer.doDoDelete() method.
Fixes the issue in OpenStack and JClouds plugins.
(issue 31098, regression in 1.618)
ClassNotFoundException.
(issue 30820)
ClassCastException in AbstractBuild::reportError() if the build step is not Publisher.
(issue 30730)
hudson.model.Executor
(PR 1712)
NullPointerException while estimating duration of Queue executable items.
(issue 30456)
SecretRewriter.
(issue 30456)
RuntimeExceptions in run retention policy handler calls.
(issue 29888)
NullPointerException in CLI if Jenkins cannot find the specified job
or a job with the nearest name.
(issue 30742)
NullPointerException for disabled builds in ReverseBuildTrigger.
(issue 29876)
hudson.Util.isOverridden() now supports protected methods.
(issue 30002)
lib/layout/task) did not assign the proper CSS style.
(issue 30787)
NullPointerExceptions.
(issue 29790)
No notable changes in this release.
NullPointerException in Executor/causeOfDeath page if
there is no exception details.
(issue 25734)
NullPointerException in AbstractProject constructor
if Jenkins nodes has not been loaded yet
(issue 28654)
NullPointerException in a build trigger
(issue 27549)
UnlabeledLoadStatistics
causing overheads in Cloud slave provisioning
(issue 28446)
CronTab API: Timezone support for scheduling
(issue 9283)
NullPointerException when trying to reset Jenkins admin address
(issue 28419)
NodeMonitorUpdater
(PR 1714)
NullPointerException computing load statistics under some conditions.
(issue 28384)
Descriptor.getId fix in 1.610 introduced regressions affecting at least the Performance and NodeJS plugins.
(issue 28093 and issue 28110)
Descriptor.getId fix in 1.610 introduced a regression affecting at least the Copy Artifacts plugin.
(issue 28011)
Descriptor.getId were not correctly handled by form binding, breaking at least the CloudBees Templates plugin.
(issue 26781)
packaging component.
config.xml file.
If you downgrade after this, your slave settings will be lost.
FilePath.chmod fails with ClassNotFoundException: javax.servlet.ServletException.
(issue 26476)
SimpleBuildWrapper API.
(issue 24673)
/manage as well.
(issue 26382)
JAVA_HOME check to work with JDK 9.
(issue 25601)
list-jobs command should display raw name, not display name, where they differ.
(issue 25338)
/signup when not possible.
(issue 11172)
secrets/master.key.
(issue 25937)
AbstractProject.AbstractProjectDescriptor#validateLabelExpression for plugins.
(pull request 1456)
Jenkins instance with internal validation
(issue 23339)
WindowsInstallerLink.doDoInstall.
(issue 25358)
FileParameters should be handled as different values to avoid merging of queued builds
(issue 19017)
OldDataMonitor.
(issue 24763)
ConcurrentModificationException in RunListProgressiveRendering.
(issue 21437)
StackOverflowError for some old SCMListeners.
(issue 23522)
OldDataMonitor.
(issue 24358)
?tree parameter instead of ?depth.
(commit)
NullPointerException from Executor.run.
(issue 24110)
set-build-parameter and set-build-result CLI commands.
(issue 24080)
<l:pane>s and making them work better with new layout.
(issue 23810,
issue 23829)
IllegalArgumentException from AbstractProject.getEnvironment when trying to get environment variables from an offline slave.
(issue 23517)
NullPointerException when ArctifactArchiver is called for a build with the undefined status.
(issue 23526)
ArctifactArchiver (.git, .svn, etc.).
(issue 20086)
NullPointerException when "properties" element is missing in a job's configuration submission by JSON
(issue 23437)
SecurityListeners.
(issue 23417)
NullPointerException caused by the uninitialized ProcessStarter environment in build wrappers
(issue 20559)
DecoratedLauncher)
(issue 19454)
NullPointerException when a build triggering returns null cause
(issue 20499)
NullPointerException on plugin installations when invalid update center is set
(issue 20031)
FileParameterValue
(issue 22693)
Slave.createLauncher.
(issue 21999)
NoSuchMethodError: hudson.model.BuildAuthorizationToken.checkPermission(…) from Build Token Root plugin since 1.556.
(issue 22382)
Trigger to be a DependencyDeclarer.
(issue 22397)
RobustMapConverter.
(issue 22398)
copy-job and create-job CLI commands.
(issue 22262)
identity.key, used to secure some communications with Jenkins, now stored encrypted with the master key.
First Last _first.last@some.org_, breaking mail delivery.
(issue 16332)
build -s -v command caused 100% CPU usage on the master.
(issue 20965)
java -jar jenkins-core.jar folder/external-monitor-job cmd … did not work.
(issue 21525)
. (period).
(issue 21639)
/login offers link to /opensearch.xml which anonymous users cannot retrieve.
(issue 21254)
SecurityListener to receive login events and similar.
(issue 20999)
Older changelogs can be found in a separate file