@rojac
I was expecting that answer … remember the tiny little WP nickname glitch I mentioned …
I think your user leak is caused by this tiny little WP nickname glitch.
Somewhere in the past the user got created. However it probably got created with username and nickname being identical (which is the default in WP).
So you changed the nickname afterwards. However the iTSec plugin was not yet installed and activated or it was but the Force Unique Nickname setting was not yet enabled.
When initially creating the user the nickname is stored in the database in 2 different tables …
The WP nickname glitch I mentioned happens when changing the nickname. WP will only save the new nickname in 1 of the 2 database tables. So the original value (which is still identical to the username) still exists in the other table…
Guess which value the user enumeration URL exposes from the database ?
Right, the unchanged original nickname value !
All of the above can be confirmed by logging into the database using phpMyAdmin and just looking at the user_nicename field value of the wp_users table for the relevant user in the database. I’m convinced it’s value is still identical to the username …
Once the above is confirmed simply edit the user profile for the relevant user and change the nickname while the iTSec plugin Force Unique Nickname setting is enabled. The iTSec plugin Force Unique Nickname setting ensures both nickname values are updated in the database.
dwinden