com_jupgrade-2.5.1 installs with ease, error free. There is a place to configure your options before clicking on upgrade. After clicking upgrade, it appears to be working, but it gets stuck at Upgrading progress... Migrating undefined. It does not work. Many people, including myself, have posted this on the support forum with no response. There is no support. If you then go to yourwebsite/jupgrade, you will be redirected to yourwebsite/jupgrade/installation/index.php which gives anyone access to install Joomla on your website. The upgrade does not finish, the Joomla installer is not removed. This leaves a security issue.