Malware is different from a virus and cannot be detected by antivirus scanners in most cases.

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
• TDSSKiller - AntiRootkit Utility
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

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

Did this fix your problems? Please report back soon.

Thank you for your reply. (FYI: The above question was posted by a Microsoft Research Engineer and me since neither of us can figure out why this is happening. So the brain-bank on this is pretty big!)

I scanned with all of the above scanners. (Thank you for the links!) I also scanned my system with Adaware, Super Antispyware, Norton Internet Security 2013, and Norton Power Eraser . . . and Kapersky v14 on the Windows 8 system)

NONE of the scanners reported anything other than the usual trackers.

Firefox was un-installed, re-installed, reverted back 4 versions and v3. Chrome shows the same result.

The Windows 8 system was wiped and restored. Office 365 was immediately re-installed and showed the SAME behavior except that the "random" 3-character URL was different . . .

. . . This extra Tab only shows up when I open any Office 2013 product to a New document or worksheet go to File>Account>Manage Account.

You are launching File > Accounts from a desktop application?

In that case, could you try changing a setting. This will help determine whether the URL is originating from the browser or from an external application.

In a new tab, type or paste about:config and press Enter. Click the button promising to be careful.

In the filter box, type or paste link.o and pause while the list is filtered.

Double click the following preference and change the value as bolded below:

browser.link.open_newwindow.override.external - for links in other programs

-1 = apply the Options/Tabs setting to external links (default)
3 = open external links in a new tab in the last active window
2 = open external links in a new window
1 = open external links in the last active tab replacing the current page

After that, you would expect a new window for office.microsoft.com and, if the second tab is generated by an external process, a second new window for that. If you still get a second tab, it suggests the request is originating from office.microsoft.com -- or some glitch with third party browsers opening that page.

Hm . . . interesting suggestion.

. . . okay, I tried ALL of the integers and regardless of which is set, I'm always getting a new window with the two tabs!

All due respect for those taking the time to consider my issue: Thanks for the speedy replies, in return I responded in kind . . . however it's late where I am [EST] and I've got work in the morning . . . I'll have a look at any other suggestions in about 18 hrs from now) . . . :)

Do a malware check with some malware scanning programs on the Windows computer.
Please scan with all programs because each program detects different malware.
All these programs have free versions.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender: Home Page:
  http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

Please consider contacting the Microsoft support team.

I had an open case# with Microsoft Support which went up a level or two . . . to where the MS Research Engineer and I composed the original post above. This very qualified engineer has closed that ticket and marked it "Unresolved". We were hoping the Firefox people could help us further.

Up until "Cor-el's" post just above posted at 3:52am, I have been following the advice here very closely. I will scan my system with the software suggested in his post above that I haven't tried yet a little later . . .

Thank you.

Another thought. Could you temporarily turn off redirection? This might allow you to see whether the initial request coming from Office 2013 is redirected and whether the second tab is opened before or after that redirect. ("Might" because this feature doesn't stop script-generated redirects.)

orange Firefox button (or Tools menu) > Options > Advanced

On the "General" mini-tab, check the box for "Warn me when websites try to redirect or reload the page"

If the initial URL redirects, you should get an infobar below the Navigation Toolbar with an Allow button. Before allowing, copy the URL from the address bar for comparison with the final URL.

Does this reveal anything different?

jscher2000: In testing I see how that option works. However it has no effect on my issue. . . . which is still interesting information!

All Malware scans completed . . . Sure . . . Junk was found and processed. Nothing major.

No change.

(sigh)

I don't have Office 2013 or an Office 365 account, and I'm running out of ideas for testing.

Does this issue occur outside your network, e.g., connecting from home not through a VPN, if that is possible?

What if you disable some of the site's scripts? You can install the NoScript extension and when you next launch the site, scripts will be blocked. Does that have any effect on the second tab opening? If it hasn't opened, you can use the NoScript toolbar icon to allow script sources (domains) one at a time (allow the page to reload in between) to see at what point you get the second tab.

(NoScript is great, but since it is paranoid by nature, you may find that you don't want to keep it for daily browsing after doing this test.)

https://addons.mozilla.org/firefox/addon/noscript/

Oh Yeah! I remember that Addon . . . used it a loooong time ago.

No effect . . .

"connecting from home not through a VPN, if that is possible?" . . . I'm not sure how to do that, but nevertheless, It still happens when I'm on a network away from home.

I still need to bring the Win 8 laptop to work and try it there. At work, it's a typical proxy server-based "Enterprise" network.

So... to summarize what I think we've learned so far:

• The second tab is generated from within Firefox; it is not a second request from Office 2013
• The second tab is not generated by an HTTP redirect
• The second tab is not generated by a script
• The second tab appears both on internal and external networks

Do you have any extensions that could be a factor? You could test using Firefox's Safe Mode. That's a standard diagnostic tool to bypass interference by extensions (and some custom settings). More info: Diagnose Firefox issues using Troubleshoot Mode.

You can restart Firefox in Safe Mode using

Help > Restart with Add-ons Disabled

In the dialog, click "Start in Safe Mode" (not Reset)

From that point, new windows which open in the same session of Firefox also should not have any extensions active.

Any difference?

Just to reiterate: The second tab opens on both my Windows 7 system on my home network (after I purchased, downloaded and installed the Office 2013 suite). It also opens on my Windows 8 laptop (no matter what network I'm on) since it was out of the box . . . After the initial setup, I opened the bundled Office 365 trial, and logged in with my Microsoft account credentials. For testing purposes, I wiped the HDD and restored the laptop, etc . . . STILL opens the extra tab, only this time it's a different 3-character URL.

. . .  So yes, at work on a typical proxy-served "Enterprise" network environment, the second tab opens as usual.

. . .  Even when Firefox opens in Safe Mode. (I confirmed it: After the second tab opened, I went to Firefox>Addons . . . and saw that the few that I have are disabled.)

Is there any place left to look? Could my MS Office installations be a wee-bit compromised??

If you switch to using IE as your default browser and compare the URL, is it the same as the first tab in Firefox, or does it have different parameters? I ask because one of my guesses was that the "random" domain was a portion of the URL that somehow got separated. (That said, I'm not sure how it could happen.)

I called the extra tab's 3 Char-URL "random" because it doesn't resolve to an existing website. 4a1 (dot) com is the one that opens on my desktop, and 54b (dot) com opens on my laptop currently. -The URL was different the first time around before I fully Restored the laptop.

re: Default Browser . . . I test to ensure that the correct browser is set as the default by opening a document in Word and create a hyperlink on the page. etc. Sure enough the correct browser opens every time. (IE, FF or Cr)

Interestingly, when a doc is open in Word and I navigate File>Account>Manage Account (as per my issue here) Firefox opens regardless of the default browser set in Windows 7 or 8.

Working in a remote session, the MS Engineer saw the above described behavior, did something and temporarily fixed it (apparently). During that time, we observed that the extra tab DID NOT open in IE, but DID open in FF and Cr.

. . . .

Hi NikonErik, I don't know why the Word menu item would open a page in Firefox even when IE is the default browser. That implies that it is not simply sending a URL request to Windows but may be building its own command line or using DDE (DDE is no longer explicitly supported in recent versions of Firefox) or some other interprocess communication. Perhaps it stores a path in its own section of the registry and stops checking the identity of the default browser in real time. If that's the case, maybe exiting and restarting Word will refresh that setting??

I wish it were that simple. By now I would have discovered that, no?

I wonder if this interesting little buggy behavior is somehow related . . .

Today I was reviewing a DVD I burned from an Mp4 file and noticed that it opened in Windows Media Player (on Win 7 pc). For reason "xyz" I want all my video files to open in a 3rd party media player I use. "Set Default Programs" doesn't show this media player for some reason, yet if I go to "Associate a File Type" I see the preferred player in the list that'll show. Fine, I can live with that, so I set the association etc.

Despite my efforts, the file STILL OPENS in Windows Media Player . . . Grrr

(Just speculation, I don't want to open/start another thread about this.)

This is making me want to stick with Office 2010.

Hopefully you will find a way to switch Word 2013 to opening the account in IE so you can compare the URLs.

Thank you . . .