in web admin almost page, you can see message like "Litespeed Web Server Enterprise 5.0.4", it's same output of
/usr/local/lsws/bin/lshttpd -v
also in Actions -> Version Manager, you can all version history installed on your server.
but no build info in webadmin at present, only /usr/local/lsws/autoupdate/build tells the build number.