The displaypost function in cgi-bin/cgi-lib/forum_display.pl in web-app.org WebAPP before 0.9.9.7 does not display usernames in conjunction with real names, which makes it easier for remote authenticated users to impersonate other users.
http://www.web-app.org/downloads/WebAPPv0.9.9.7.zip
http://www.web-app.org/cgi-bin/index.cgi?action=forum&board=how_to&op=display&num=9458