Opera released version 12.01 which contains some recommended security updates. Information regarding security and stability enhancements for the various version are available here: Windows changelog, Mac changelog, Unix changelog.
http://www.opera.com/docs/changelogs/windows/1201/
http://www.opera.com/docs/changelogs/mac/1201/
http://www.opera.com/docs/changelogs/unix/1201/
https://ssl.opera.com:8062/desktopteam/blog/2012/08/01/opera-12-01-security-and-stability-release
Reference:
http://www.dshield.org/diary/Opera+Security+Update/13825