The squared area above is a place for a partner's advertising banner managed by a "3rd party code" loaded as a secure Plugin created with the Jailed library. The Plugin runs in a sandboxed Worker and cannot access the main document, with except for the two methods explicitily exported by the application: for changing the url the banner is pointing to, and for changing the banner image. Even if the Plugin performs an attempt to set too big image, it will be cropped by the application. The Plugin is fully controlled by the application and may be connected or disconnected anytime (operated with the two buttons in this demo).