Opera contains a flaw that may allow a malicious user to disguise the location of a web page. The issue is triggered when the onUnload body attribute is used to change the address bar information without leaving the current page. It is possible that the flaw may allow malicious web site operators to misrepresent their content as someone else's, resulting in a loss of integrity.
Upgrade to version 7.50 or higher, as it has been reported to fix this vulnerability. An upgrade is required as there are no known workarounds.