Opera before 11.00, when Opera Turbo is used, does not properly present information about problematic X.509 certificates on https web sites, which might make it easier for remote attackers to spoof trusted content via a crafted web site.
http://www.opera.com/docs/changelogs/windows/1100/
http://www.opera.com/docs/changelogs/unix/1100/
http://www.opera.com/docs/changelogs/mac/1100/
http://secunia.com/advisories/42653
http://lists.opensuse.org/opensuse-security-announce/2010-12/msg00006.html