Edit There is also an officially reported and assigned bug known to cause this problem, as I mention in other posts downthread; and discussed intensly in Mozilazine - Mulitiple Instances Of plugin-container.exe; although the bug is unlikely to be given a high priority fix.

There is a possibility this is malware, or maybe just aggressive advertising. Another possibility is you are a user that favours keeping hundreds of tabs open, and inevitably they include video etc content opening multiple plugin container.exe.

The plugin container is designed to help see What is plugin-container, there are ways to modify the behaviour of plugin container, but you probably need to first of all try to work out what all these are.

at the most I have three tabs open at any one time. it can happen when I open firefox as it did this morning. booted up pc and waited until everything had finished doing what it had to do then started firefox. out of curiosity I then checked with task manager.I had nine versions of plugin container running by the time my home page (virgin media) had finished loading.

I have re run the firfox install program (after shutting don firefox) and then tried again. at present I have two tabs open, my home page and this one. a check of task manager shows only one version of plugin container running. I try running my anti malware program and doing a full system virus check to see if anything turns up.

Hey, this happens to me too, I dont know why it does it but It does it no matter whether in safe mode or not.

Im glad to see its not just me who has the problem because I run FF4 sandboxed with sandboxie (isolates browser files from infecting system in case of malware)

Its not malware its a bug, heres a link to it in fact... http://forums.mozillazine.org/viewtopic.php?f=38&t=2140631

Im on windows 7 64bit btw, other thing is that it happens like one in two times for me, sometimes when I close it it will multiply, sometimes when I start it up...

found this on an info page about plugin container exe.

Plugin-container

An out-of-process plugin runs in a separate process named "plugin-container" ("plugin-container.exe" on Windows). For each plugin for which the "OOPP" crash protection feature is enabled, a separate plugin-container process will be started when you first visit a webpage that evokes that plugin. When you exit Firefox, those plugin-container processes will terminate.

it still does not explain why it multiplies when you shutdown firefox.

From my understanding of the thread about the bug the problem is that Firefox 4 (and possibly firefox3.5-6) is opening these additional plugin containers whilst it is clearing cookies.

If my understanding is correct then a potential workaround if your system has a critically low memory availability will be to avid any actions leading to firefox having to clear cookies especially the LSO s used by FlashPlayer. You will note that apparently Firefox will open these plugin containers for this purpose even if the plugin itself is disabled.

I suspect this sort of problem is not going to get a high priority fix.

I've had the same problem and noticed that if you clear recent history using Firefox it will open the containers while clearing OR if you clean cookies using a different program like CCleaner, it will open the plug-in containers automatically the next time you start Firefox. It's opened up to 32 plugin container processes at one time on my system and I am not short on memory but it still freezes up my computer pretty bad so; when the containers open like that close Firefox by using the "Exit" function in the browsers "File" drop down menu, let Firefox close itself out and all the containers (you can watch them close out in the task manager to make sure it is closing them all and it's not always quick). The next time you open Firefox it should load normally without the extra containers. It SHOULD stay that way until you clear your cookies again, at least it has for me thus far.

Force closing Firefox from the task manager can also cause it to open multiple containers so try getting the browser to fully close itself out instead of force closing the firefox.exe or the plugin-container.exe's.

Not sure if this helps but it seems to be the only way I can get Firefox to run without all those plugin containers bogging down my system.

If you are having this problem it may be worth adding a vote on the current thread to confirm you have the problem. I note this also occurs on firefox5 and 6. The bug fix will probably not be considered a high priority.

Another workaround will be to use absolutely minimal plugins, possibly by using another OS account. (rather extreme but remember this fault is firing up even disabled plugins).

As a temporary session fix remember also you can close down / kill each individual plugincontainer processes without exitting firefox (eg use task manager) that should allow you to continue the session, until you try clearing history / cookies.

I just now noticed this same problem happens with mine. As soon as I clear my private data my computer immediately acts like its processing something and 3+ plugin-container.exe tasks open up.

I've run virus scan's on all the paths that these plugin-container.exe's are coming from. None are infected with a virus that my Microsoft Security Essentials was able to detect. Additionally every site I check seems to all the more prove that mine are connected with this bug where (sometimes) when the browsing history is cleared it opens up several plugin-container.exe's. Although only one of them seems to be directly linked with my Adobe add-on. All the other's end in something related to PC-doctor for Windows XP. I've thus scaned PC-doctor files and found no threat. All the more this seems like just an annoying bug rather then a potential threat.

This will presumably potentially affect all firefox users (of reent firefox versions who use plugins and clear cookies) but either users are not identifying this or are not too concerned about it. The bug itself is not collecting many votes. This thread is only currently showing 39 users as having clicked to say they have the problem.

@John99

I agree, since most people probably have such fast computers they probably never bother to even look at their current processes. I myself only do as an extra measure to insure I have a safe computer. I've noticed though that this bug doesn't happen all the time either. Sometimes I can clear the data & none open.

I'm not using Firefox until this is fixed. I uninstalled completely, deleted everything, and reinstalled, and it's giving me the same problem. It can't find my home page, refuses to start a new session, hangs up on everything... this is not a minor issue, this prevents Firefox from even running. There's no reason for it, either, since it was working just fine before.

Hi Not_Needed,

I am not sure you have the same problem.

It is easy to reinstall the old version 3.6 instead of firefox 4 if that makes you happier. see

• installing a previous version of firefox

You would probably do better to start your own question explaining exactly what problems you now have.

An update on my end now is that this bug seems to occur every time now. Although I'm not low on memory so it doesn't effect me to much. I'd still of course like it fixed although for the time being it isn't limiting my use of the browser.

Sorry, for those who have not figured this out. You have an invasive program called Superfish. You need to delete Windows shopper from plugins list and remove both windows shopper and superfish from your computer. Including the registry through "regedit". This was the only change made on my computer and Firefox now runs without a flaw, and only 1 plugin container. Hope this helps others.

Lt.Carter,

There is a known bug, and I see no indication that is fixed. What you see could well be a different problem.

Removing entries with "regedit" may not be a wise move for the ordinary user.

I agree with John, in addition I've run numerous scans on my computer. If I had a virus I'm positive MSE would have found it. As a matter of fact upon visiting a certain site today my MSE immediately found an adware threat just as it entered my temporary internet files folder. Upon which it easily removed it and have had no problems since.

Your correct there may be a bug or a variety of problems. However i read the above messages. Reinstalled Firefox and used a registry fixing program to no avail. The plugin containers just kept multiplying. As stated above it does not matter if it's deleting cookies or closing Firefox or going to multiple sites, they just kept multiplying. After doing what i said above the problem is "TOTALLY" gone. I just spent the last 5 hours online with no problems or system lags. You are correct though, if you do not feel comfortable editing the registry, try simply uninstalling windows shopper and deleting the files called superfish. That may do it. P.S. this is my experience not a system fix for Firefox. But it may help someone with the same predicament.

I'm thinking of making my own discussion on this since my problem & that of a few other's isn't exactly the same as the one this thread is on. For me the plugin containers only multiply when I clear my history on firefox. In addition as I said before it doesn't happen ever time. Just now as a matter of fact I cleared my private data and no additional plugin-container.exe's opened. Although even when they do with the 1.5 gigs of RAM I have, unless there were more then 10 open it doesn't really effect my computers performance. It is a minor bug and probably wont get fixed for sometime.

I'm sorry you do not understand. I myself run a full system scan at the end of every day"2hrs 43min". An invasive program is not a virus or spyware or even phishing. It is a program that is loaded on your computer without your consent or knowledge and has a negative impact on your system or specific program(s). Not your anti-virus program nor mine for that matter will ever recognize this. Windows shopper w/ Superfish is one such program, it affected my Firefox with the exact same effect as "evilsid" in the original post above.