Opera Software has released a new version, 11·11, of its Opera Web browser for all platforms (Linux, Mac OS X, Windows, Free BSD, and Solaris). The new version incorporates a fix for a serious security vulnerability; it also fixes a number of stability problems and other bugs. Full details of the changes are given in the change logs for Windows, Mac OS X, and UNIX-like systems.
I recommend that you install this update as soon as you conveniently can, because of its security content. You can get the new version via the built-in update mechanism (Help > Check for Updates), or you can download an installation package.