The remote host is vulnerable to an HTML Injection attack.
The remote host is using a version of Opera that is prone to a security flaw where a malicious attacker can inject malicious data into a URI. Such an attack would require that the attacker be able to convince an Opera user to browse to a malicious URI. Successful exploitation would result in the attacker gaining access to confidential data (such as authentication cookies) or executing code within the browser.
Upgrade or patch according to vendor recommendations.