QUOTE
A vulnerability has been identified in Opera, which could be exploited by remote attackers to crash a vulnerable browser or potentially take complete control of an affected system. This flaw is due to a memory corruption error when processing a CSS "background" property containing an overly HTTPS URI, which could be exploited by attackers to cause a denial of service or execute arbitrary commands by convincing a user to visit a specially crafted Web page.
See http://www.frsirt.com/english/advisories/2006/2987