Crisis over, it seems it was from VaultPress plugin:
> Could your plugin have made a file in the root of my wordpress install
> called wp-config-db.cnf.php ?
>Yes -- we use this file to pass MySQL credentials to your MySQL process during restores. If you're concerned about it, you can delete it, and we'll regenerate one when we attempt a restore.
Best,
ChrisAutomattic | WordPress.com | VaultPress