[Plugin: Password Protect WordPress] not support Mutil Site

when wordpress enable Mutil Site option
SubSite A and SubSite B enable Password Protect WordPress plugin but difference password,

a client user login to Subsite A used Subsite A’s password and don’t need Subsite B’s password can into Subsite B.

http://ww.wp.xz.cn/extend/plugins/password-protect-wordpress-blog/