You may be seeing scam messages trying to seduce you to install malware. You can check in Help > About if you have the latest Firefox 23.0.1 version. You can find the full version of the latest Firefox 23 release in all languages and for all Operating Systems here: *http://www.mozilla.org/en-US/firefox/all.html Note that some security software can block the stub version of the Firefox installer, preventing you from updating. ---- Do a malware check with some malware scanning programs on the Windows computer.<br> Please scan with all programs because each program detects different malware. Make sure that you update each program to get the latest version of their databases before doing a scan. *Malwarebytes' Anti-Malware:<br>http://www.malwarebytes.org/mbam.php *SuperAntispyware:<br>http://www.superantispyware.com/ *Microsoft Safety Scanner:<br>http://www.microsoft.com/security/scanner/en-us/default.aspx *Windows Defender: Home Page:<br>http://www.microsoft.com/windows/products/winfamily/defender/default.mspx *Spybot Search & Destroy:<br>http://www.safer-networking.org/en/index.html *AdwCleaner:<br>http://www.bleepingcomputer.com/download/adwcleaner/<br>http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml *Kasperky Free Security Scan:<br>http://www.kaspersky.com/security-scan You can also do a check for a rootkit infection with TDSSKiller. *Anti-rootkit utility TDSSKiller:<br>http://support.kaspersky.com/5350?el=88446 See also: *"Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

This was continued in a new thread here: [https://support.mozilla.org/en-US/questions/970377 Upgrade popup (#970377)]