v. 11.0.2 of what? The current Firefox release version is 49.0.2, which you used to post here.

Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• Anti-Rootkit Utility - TDSSKiller
• AdwCleaner (for more info, see this alternate AdwCleaner download page)
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista if you don't already have one. Windows 8/10 have antivirus protection built-in.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Did this fix your problems? Please report back to us!

My mistake, apologies, my update is 49.0.2!

Shouldn't my Kaspersky Total Security remove this malware for me? I did have MalwareBytes installed prior to installing Kaspersky, and they advised me to uninstall Malwarebytes, since they covered it?

I also had MSN Security Essentials until they told me last year that they would no longer be supporting it with updates!!!!!!!!!!!!!!!!!

So, I await your further thoughts, and thank you for your rapid response above.

In some cases, this might be caused by ads in the page. In other cases, it might be caused by a bad add-on.

After the Refresh, did Firefox ask whether you want to activate any extensions? You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Extensions. Then cast a critical eye over the list on the right side. All extensions are optional. If in doubt, disable.

Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Any improvement?

You also could consider using an ad-blocking extension if sites are displaying ads irresponsibly. This one is often recommended:

https://addons.mozilla.org/firefox/addon/ublock-origin/

Thank you for your suggestion which I think might have solved it. I found the rogue Foxstart in the extensions and removed it, which seems so far to have stopped the problem? Time will show!

Sorry, I spoke too soon! It's still around so there must be something else, as the only extensions remaining are my Kaspersky pair?

Do you notice any pattern to the sites that generate the pop-ups?

Have you considered using an ad-blocking extension?

I have installed your recommended ublock extension which seems to have improved matters. Let's see what happens, but thanks again for your assistance. Much appreciated.

I am disappointed to have to report that the problem is still with me, despite having, as stated, already got Kaspersky, refreshed FF, checked & disabled unwanted extensions, installed Ublock. Furthermore, I am surprised that FF or Ublock does not include a simple facility to individually block unwanted websites e.g. by initially displaying a warning dialog box & asking if one wished to allow it, or by right-clicking on them & selecting a blocking command?

Further suggestions urgently please?

It sounds as though you are doing all the things that would help. Either you are reading websites that have annoying advertising on them, or there is still an issue with extra ads launching that have nothing to do with the site, injected either by an add-on, or other software, or on the way to your computer.

Did you want to try some of the supplemental scanners listed earlier in this thread? Most can be run a single time and then uninstalled and will not interfere with Kaspersky. Security software companies often have different criteria for what is annoying vs. what is malicious, so they might help.

Another thought: does the article where these ads launch from have a Reader View icon in the address bar? In Reader view, sidebars and distractions are stripped away. Sometimes part of the article also is missing, and in that case it won't help you, but maybe it will bypass the problem on some sites.