For users who are using a template override for design/standard/templates/content/datatype/edit/ezuser.tpl, is it mandatory to use the |wash() template operator in the {$attribute.content.login}.
You can see the use of the |wash() template operator in the following code snippet: {$attribute.content.login|wash()}.
Important: Please also be aware of the fact that now eZ Publish strips tags from the user login names.
In order to find user accounts with suspicious login, please, use the disablesuspicioususers.php script. This script has two options: