Just a couple of days after releasing version 10.52 of the Opera browser for Windows and Mac OS X, Opera Software has released another new version of the browser, 10.53, also for Windows and Mac. This update addresses a specific security vulnerability , rated by Opera as “extremely severe”. The (brief) Release Notes are here.
The new version should be available via the built-in update mechanism (main menu: Help / Check for Updates), or it can be downloaded here. Because of its security content, I recommend that you install this update as soon as you conveniently can.