hi dj, unfortunately this is a scam tactic that is trying to trick you into installing malware, so don't download or execute this kind of stuff! only download firefox from its official location at mozilla.org - in addition updates are handled automatically by firefox so you don't have to download anything (you can initiate a check for updates in the firefox ''menu ≡ > help ? > about firefox''). in case this is caused by rogue advertisements on legitimate websites, you could install an adblocking extension in firefox: https://addons.mozilla.org/firefox/addon/ublock-origin/ you might also want to run a full scan of your system with the security software already in place and different tools like the [https://www.malwarebytes.org/antimalware/ free version of malwarebytes], [https://toolslib.net/downloads/viewdownload/1-adwcleaner/ adwcleaner] & [http://www.kaspersky.com/security-scan kaspersky security scan] in order to make sure that there isn't already some sort of malware active on your system that triggers these false alerts. [[Troubleshoot Firefox issues caused by malware]]

philpp, thanks I suspected it was a scam. I installed yesscript and it has stopped the pop up. The web site were I encountered this problem still works good with only one inconvenience that is easy to work around dj