This is a more secure way to log in to phplist. It also eliminates the need for administrators to keep separate login information in the phplist system.
Place CosignPlugin.php in your plugins directory.
This directory may be different for different installs.
By default, the directory will be [site-root]/lists/admin/plugins
External requirements: This plugin requires the following additional components that must be installed separately:
Navigate to the phplist settings page and fill in your logout URL.
It is under the cosign section.