If you are not using LDAP, then it is probably not the case. Anyway, here is the link https://igniterealtime.org/downloads/download-landing.jsp?file=openfire/openfire _3_9_1.exe
It should work by just uninstalling 3.9.3 and installing 3.9.1 (i did this on my test box). But you should of course do a backup of your current installation (stop Openfire and copy whole C:\Programs Files\Openfire\ folder),