After updating to Credentials Plugin 2.0.1 (Currently using 1.28), we are unable to create a new Dumb Slave / Permanent Agent and we're also unable to modify any existing agents. The only node that can be successfully modified is 'master'.

Steps to Replicate

• Install Credentials Plugin 1.28
• Update plugin to 2.0.1 and restart the Jenkins service
• Once Jenkins is back online, http://<JENKINS_URL>/computer/new
• Provide a name and choose "Dumb Slave" (Jenkins 1.x) or "Permanent Agent" (Jenkins 2.x), press OK
• The page will sit in a loading state and never return the next screen.

Additionally, the same result will occur if you find a node and choose "Configure" for it.

Workaround

• Downgrading the plugin back to 1.28 and restarting the Jenkins service resolved the issue.

This was tested on both Jenkins 1.650 and 2.6. I could not locate any errors or messages being reported to jenkins.log around this behavior .