[wp-testers] update.php in wp-admin?

[[BLT]FQX]

In the plugin page, wp told me that there is a plugin need to be upgraded,
and a new link to wp-admin/update.php
The update page needs my FTP information.
That is odd, because OneClick Installer can do the same thing without any
FTP support.
Can any one tell me more about this update.php ?