xchat/hexchat: does not verify the server hostname matches the domain name in the subject's Common Name (CN) or subjectAltName field in X.509 certificates
The ssl_do_connect function in common/server.c in HexChat before 2.10.2, XChat, and XChat-GNOME does not verify that the server hostname matches a domain name in the X.509 certificate, which allows man-in-the-middle attackers to spoof SSL servers via an arbitrary valid certificate.