What security software do you use that is reporting viruses in the Firefox update? Can you post a list of what is detected (either in text form or a screen shot from the program's alert dialog or log file).

I suggest supplementing your regular security software with scans using the tools in this article to see whether you have a third party "updater" running in the background that is quietly sneaking new software onto your computer along with the Firefox updates:

Troubleshoot Firefox issues caused by malware

In order to avoid data loss during the cleanup process, please make a backup of your currently active Firefox settings (your Firefox profile folder). This article has suggestions on that:

Back up and restore information in Firefox profiles

Ok try this: 1. uninstall firefox 2. hold down the windows key and press R 3. then paste or type this: %temp% 4. delete everything inside (don't worry you wont effect any important or windows files at all) 5. try installing mozilla again from the official website. Good luck :)

Here is a screen shot from AVG (virus protection software). All of this showed up during the Firefox 28 install.

I have deleted my temp files and will try reinstalling Firefox 28

You can ignore tracking cookies as those are usually harmless and only allow websites to track you activity.

• http://en.wikipedia.org/wiki/HTTP_cookie

Try to boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test to see if this helps to install Firefox if security software is currently blocking this.

I have reinstalled firefox 28 and after a number of trials of various things, the only thing I found is my AVG antivirus toolbar seems to crash Firefox when it is enabled. What happens is when I set google to my default page and enable the AVG toolbar (it has a secure search function). When I restart firefox my AVG software popups with a warning "AVG has prevented a program from changing the default search program" and at that point firefox never opens again. I have now reinstalled firefox28 and uninstalled the AVG safesearch toolbar. I guess time will tell if anything else happens. My next step is to reinstall my profile from backup, hopefully that does not cause any issues!

You will have to disable or uninstall extensions that causes Firefox to crash.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Hi Tom, thanks for the screen shot. Normally, when you download the Firefox installer, it has a file name like the following:

Firefox Setup 28.0.exe

So if you aren't getting that download from the official site, please check here first in the future: https://www.mozilla.org/firefox/all/

By the way, those cookies in the screen shot are in the Windows/IE cookies folder. Firefox doesn't use that folder for Firefox cookies, but plugins and add-ons might use it.

Same problem here, only with Vista. For the jillionth time I am trying to get 28 downloaded so it will open. Using the internet explorer as my downloading browser, I switched my homepage to blank. Maybe that will make a difference? We'll see.