Weird character before custom link

Dear support,

My domain is as follows:

http://www.abc.com/

by using this plugin, i should be able to customize my login page url to something like:

http://www.abc.com/login/

However, when using this plugin, there is part of the link i cannot change:

http://www.abc.com/?

There is a “?” out of nowhere that i cannot remove.

Please help.

https://ww.wp.xz.cn/plugins/wps-hide-login/