Chromes auto-fill , populates the username and password of any user who has logged in to Jenkins into the 'bindName' , 'bindPassword' field in the Advanced section of 'Active Directory' under Configure Global Security .

As a result , on saving this ( without noticing ) , no users are able to login .

The only way to fix this was to manually edit the config.xml to remove the erroneous <bindName> and restart the Jenkins instance .

Am calling this a bug due to the disruptive nature of the issue ( which called for a restart of the Jenkins service )

This happens silently as the 'Advanced fields' are not expanded and thus not seen by default .

Autocomplete/autopopulate should be blocked for the fields in Active Directory plugin to prevent such cases .

Thanks
Taher .