According to Opera's advisory and Secunia's alert-type advisory the vulnerability exists in the way of handling Torrent files.
The code execution is possible when handling malicious Torrent files.
Download link is the following:
http://www.opera.com/download/
Reportedly only Windows versions are affected.
UserAgent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8.1.3) Gecko/20070309 Firefox/2.0.0.3
