How to Uninstall jSecure Authentication:
To remove the code by manually, please follow the below steps
1. Login to mysql through phpmyadmin or whatever you use
2. Search for “jsecure” with following SQL:
* SELECT * FROM jos_plugins where element = ‘jSecure’

1. Delete the row
2. Remove following jSecure files:
* /plugins/system/jsecure.php
* /plugins/system/jsecure.xml
Thank You.