What anti virus package are you using? VirusScan Enterprise 8 with the latest updates detects nothing. The only reference to editor.css (the [1] is added by your PC when it's downloaded) is for TinyMCE, and the css file has no trojan in it - I've checked it myself and scanned it using various online AV services.
UPDATE: Had a dig around, and found this:
http://forum.joomla.org/viewtopic.php?t=248065
It's not uncommon for the simple av scanning in some products to find what they think is a trojan/virus, when there isn't. I've had it happen myself - a few years ago I lost a bunch of .BAT files that were created by Visual Basic 6 for compiling apps I'd written because a VirusScan update detected them as trojans, just because they had "setup1.exe" in them - setup1.exe being the standard MS executable for packaging with VB application installs.
Thanks for reporting this though, if it had been a real infection then we would right now be taking all possible steps to clean it and prevent it happening again. Hopefully you'll be able to get an update from your AV vendor to fix this error.