The update patch was to fix some vulnerabilities found in the 7.0 release that were found by: sec.graymagic.com . All vulnerabilities were fixed within a day after their publication.
MiniD, Opera has the ability to identify itself as Internet Explorer 6, because some websites limit content to non-IE or Netscape (Mozilla) users. Opera can identify itself as IE 6, 3 different versions of Netscape, or as Opera. By default it identifies itself as IE, and that did play a role in one of the security bugs that was fixed.
Actually, sec.graymagic.com is a good read for security minded system administrators and users alike. They have found scores of vulnerabilities in all of the major browsers. There are several serious flaws in IE still open that they have identified.