Opera before 10.00 does not properly handle a (1) '\0' character or (2) invalid wildcard character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A6444
http://www.opera.com/support/kb/view/934/
http://www.opera.com/docs/changelogs/windows/1000/
http://www.opera.com/docs/changelogs/solaris/1000/
http://www.opera.com/docs/changelogs/mac/1000/