Advisory: Carefully timed reloads, redirects, and navigation can spoof the address field
The address field should always show the address of the page that is being displayed. Certain types of navigation, combined with reloads and redirects to a slowly-responding target site can cause the address field to show the target site's address, while the attacking site is still being displayed.
Opera Software has released Opera 12 and Opera 11.65, where this issue has been fixed.
Thanks to Jordi Chancel for reporting this issue to Opera Software.