User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:18.0) Gecko/20100101 Firefox/18.0 Build ID: 20130107224407 Steps to reproduce: Visit a Web page containing Flash content (that you haven't visited before, it seems to remember your preference for certain pages at least). Actual results: Firefox opened the click-to-play thing on the address bar which asks "Would you like to activate plugins on this page?" Expected results: Firefox should have kept the address-bar thingy closed. 99% of the time that I'm not on YouTube, the answer is no. I know where the plugin icon is, and I'll click on it if I want to activate Flash. There should at least be an option in about:config to disable this annoying behaviour.