I do not think it should do. If you had not mentioned the plugin container I would have thought that maybe you were going to a site that offered HTML5 as an alternative and that was playing.

Does this actually play a video when this happens ? and does the video stop if you kill the plugincontainer process ?

Hi John - Actually, my computer just freezes up when it happens. I'm beginning to wonder if it has something to do with Nitro Reader, which I have installed. A possibility?

Does this also happen on the Adobe test page?

• http://www.adobe.com/software/flash/about/
• http://helpx.adobe.com/flash-player.html

Note that websites can embed other media players.

Does this still happen if all plugins are disabled?

You haven't provided any troubleshooting and plugin data, so we can't check for other possibilities.

@Cor-el - not sure what additional info I can provide. Nothing happens on the Adobe page - it just says the plugin is disabled (which must mean it can detect that there IS a plugin?). I am not running any background programs and do not have anything that would seem to be related activating on startup. Again, it may have to do with Nitro Reader, although I didn't find anything relating o Flash in the program properties or control panel. All of my plugins are disabled when this occurs.

Obviously this problem is one being ignored by Firefox. It appears that some webpages have an built-in Flash auto-initiate code that will launch plugincontainer.exe even when you have the Flash add-on disabled. Firefox will then often freeze up your computer for about 15-20 seconds. Annoying, to say the least.

When posting the question initially you had a prompt to add trouble shooting information and an easy option to do so, using an addon.

If you now add such information by pasting your troubleshooting information into the next reply it may help us.

• Use Firefox button -> Help -> Troubleshooting Information -> [Copy text to clipboard]

(Or alternatively start another question using /questions/new and this time take-up the option to include troubleshooting information. Post back here to confirm if you do that).

What are the websites that you see this problem on ? Please give a couple of the web addresses.

I doubt that you see the Flash Player plugin if the Adobe test page confirms that Flash is disabled.

It is likely that you see another plugin getting activated if there is a plugin-container process started or otherwise possibly you see the built-in HTML5 video player or the built-in MP3 media player that comes with Firefox 21.

Obviously I haven't kept track of the websites where it happens, but here's a website where this occurred:

http://www.textndata.com/forums/outlined-numbered-lists-223944.html

Hope that helps.

I usually have a script blocker and turning that off I note the site you mention has re-directs and advertising including embeded .swf.

If specifically I only disable Flash ad links remain, but I did not notice any mystery plugin container, unless I had FlashPlayer active. The site does not give away much information about itself, but presumably benefits from advertising to site visitors.

I'm not seeing any Flash objects on that page with the Flash plugin disabled.
Note that the code that is used may be using possibly animated images or a JavaScript slideshow instead of a Flash object when Flash is disabled.