because the document‘s frame is sandboxed and the ‘allow-scripts‘ permission is not set

For Jenkins hosted on Ubuntu:

1. put to /etc/default/jenkins

   JAVA_ARGS="${JAVA_ARGS} -Dhudson.model.DirectoryBrowserSupport.CSP=\"\" "
   

2. visit http://<your jenkins hostname>/safeRestart

(about this and other options: https://wiki.jenkins.io/display/JENKINS/Features+controlled+by+system+properties)

UPD: this time when I did this the visiting /safeRestart was not enough. I had to do sudo service jenkins restart.

https://*.com/questions/34315723/jenkins-error-blocked-script-execution-in-url-because-the-documents-frame

Jenkins: because the document's frame is sandboxed and the 'allow-scripts' permission is not set