Almost certainly malware. A common one at the moment has an orange splash screen and a Firefox logo offering firefoxupdate.exe or something similar. That is not from Firefox (Mozilla), should not use the logo and is no doubt malware. Are you able to determine which site causes this to appear ? To check for genuine updates see * [[Update Firefox to the latest version]] You may already be on the latest version Fx47.0.1 or Fx47.0.0 (I you are on the slightly older one you will get a genuine update to Fx47.0.1 after you check)