Indeed, this seems to be specific to matrix jobs. From the Jenkins log:

May 12, 2016 12:13:23 PM hudson.model.ParametersAction filter
WARNING: Skipped parameter `MY_PARAM` as it is undefined on `some-matrix-job/SOME_AXIS=foo`

You sunk my battleship! Er, I mean, broke all my matrix jobs!

I notice freestyle jobs still work

Yes, I confirm exactly the same log entries for me:

May 13, 2016 8:30:12 AM WARNING hudson.model.ParametersAction filter
Skipped parameter `TRIFFID_FILE` as it is undefined on `MatrixParamsTest/platforms=linux-libc6.11-amd64`. Set `-Dhudson.model.ParametersAction.keepUndefinedParameters`=true to allow undefined parameters to be injected as environment variables or `-Dhudson.model.ParametersAction.safeParameters=[comma-separated list]` to whitelist specific parameter names, even though it represents a security breach

Adding -Dhudson.model.ParametersAction.keepUndefinedParameters=true to my JAVA_ARGS lets my matrix job see the parameters!

Just to add 2cents on the severity of this:

rm -rf $OMERO_DATA_DIR/*

reduced to:

rm -rf /*

And removed all files that the Jenkins users had access to.

jamoore yikes! my condolences!

jamoore Oh shit. I'm sorry that happened.

To everyone experiencing this issue: No need to downgrade, use the system properties mentioned in the warning quoted in an earlier comment to disable this new behavior, at least for a time, while plugins are adapted.

hiddenmaverick: This is a bug report for the matrix plugin (multi-configuration project type); if you're having an issue with another plugin, please file a separate issue.

I upgraded to Jenkins 2.4 and my matrix jobs just stopped working!

So trying to look into fixing this - I guess it would make sense to have a child build-specific EnviromentContributor look at getAllParameters() in the child build, see which ones (a) aren't also in getParameters() for the child build and (b) are in the parent's getParameters(), and then add any that satisfy both criteria to the environment. Does that seem reasonable?

I don't know anything about feasbility but based on our experience most safe would be to fail if there are any parameters not satisfying both criteria as if `set -u` were set in bash:

/tmp $ cat test.sh
set -u
ls $OMERO_DATA_DIR/*
/tmp $ bash test.sh
test.sh: line 2: OMERO_DATA_DIR: unbound variable

Proposed fix: https://github.com/jenkinsci/matrix-project-plugin/pull/36

Code changed in jenkins
User: Antonio Muñiz
Path:
src/main/java/hudson/matrix/MatrixChildParametersAction.java
src/main/java/hudson/matrix/MatrixConfiguration.java
http://jenkins-ci.org/commit/matrix-project-plugin/c684cc64bc16f37d45b3b704eab1324c46dd2868
Log:
JENKINS-34758 Parameters visibility in child builds (SECURITY-170)

Code changed in jenkins
User: Antonio Muñiz
Path:
src/main/java/hudson/matrix/MatrixChildParametersAction.java
src/main/java/hudson/matrix/MatrixConfiguration.java
src/main/resources/hudson/matrix/MatrixChildParametersAction/index.jelly
http://jenkins-ci.org/commit/matrix-project-plugin/55d2a6cdb62601ec51dbeff8d7ad20f6bb726455
Log:
JENKINS-34758 Parameters must be shown in the child build page

Code changed in jenkins
User: Oliver Gondža
Path:
src/main/java/hudson/matrix/MatrixChildParametersAction.java
src/main/java/hudson/matrix/MatrixConfiguration.java
src/test/java/hudson/matrix/MatrixProjectTest.java
http://jenkins-ci.org/commit/matrix-project-plugin/d9e5c847afef3928441bdb91df37f764ea6617fd
Log:
Merge pull request #36 from amuniz/JENKINS-34758-fix

JENKINS-34758 Parameters visibility in child builds

Compare: https://github.com/jenkinsci/matrix-project-plugin/compare/510aa05c7909...d9e5c847afef

Released as 1.7

Issue JENKINS-35330 describes that the content of "List subversion tags and more" and branch parameters of the Git plugin are not passed to the child jobs (I.e., as "null"). I think, the the applied fix should be revised for this types of parameters. Therefore, I've setup a link between these two issues and re-opened this issue ...

Best regards from Salzburg,
Markus

Reassigning, after it got assigned to me by mistake.

Hi Team,

Any update on this issue. Am stuck with the same problem. Jenkins version: Jenkins ver. 1.651.3

I believe this is still the case on 2.176.2.

This bug was fixed and released in matrix-project 1.7 back in 2016. If you are seeing a similar issue, please open a new jira.