We recently installed the testlink plugin (https://wiki.jenkins-ci.org/display/JENKINS/TestLink+Plugin), which required a restart of the Jenkins web front end. Upon startup, a significant subset of our job configurations were immediately corrupted. And we also found that if we reverted the job configurations on disk (from version control) and told Jenkins to reload the configuration on disk, as soon as we navigated into a job in the UI, the corruption occurred again. Only some of our jobs were susceptible though.

Uninstalling this plugin prevented this from recurring, so we are pretty sure it is the culprit.

The reason we initially investigated the testlink plugin as the potential culprit was that the job xml files had changes like:

-      <values class="linked-list">
+      <values class="hudson.plugins.testlink.testng.Class.list">

And it seemed the bulk of the content under the <metadata-tree> element that sat under that ended up being replaced, and looking substantially different. But, what was even more damaging was that all our child elements disappeared under <builders>, <publishers> and <buildWrappers>, and there was no reference at all to testlink in those areas of the job configuration.

I see that the v3.10 version of Testlink from Dec 2013 is only claimed compatible with Jenkins 1.509 (per Compatibility Matrix). But the really bad thing is that it just silently corrupts jobs during Jenkins startup, and jobs that have nothing to do with TestLink.