User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:24.0) Gecko/20100101 Firefox/24.0 (Beta/Release) Build ID: 20130911164256 Steps to reproduce: On 64-bit Ubuntu with recent updates (Firefox v. 24.0, Shockwave Flash v 11.2. r. 202). Go to YouTube.com or Facebook.com or many other sites (e.g. news sites). Actual results: If you go to Facebook, near the address bar, on the left, a plugin icon (lego brick) appears, if it is clicked a message appears: '"Adobe Flash" is enabled on site facebook.com'. and two buttons "block plugin" and "continue allowing" - clicking on either of those does nothing. Flash applications work on those sites (e.g. youtube videos work on YT). Expected results: The icon should disappear - it wasn't there before last update (Ff v. 23 -> 24.0). It implies some kind of a bug with plugins or plugin controls.

For your record, it's the doorhanger for the click-to-play feature.

This is by design. The icon is there to show users that they are using external software to render the site, and give them the option to disable that software. The "Block plugin" button should work on reload: it currently doesn't work immediately because of bug 883404.