wp-admin can't not be found after auto upgrade to 4.2.3

Hi there,

I am using litespeed 5.0.3 on my server.
Recently some of my wordpress websites performed an auto update to version 4.2.3 and after the update none of them can use /wp-admin/ or /wp-login.php to access the admin panel. The page shows “404 page not found”.

Anybody has the same problem as I do?
Any help would be much appreciated.

Many thanks.