Opera before 10.54 on Windows and Mac OS X does not properly enforce permission requirements for widget filesystem access and directory selection, which allows user-assisted remote attackers to create or modify arbitrary files, and consequently execute arbitrary code, via widget File I/O operations.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11950
http://www.vupen.com/english/advisories/2010/1529
http://www.securityfocus.com/bid/40973
http://www.opera.com/support/kb/view/962/
http://www.opera.com/docs/changelogs/windows/1054/