Firefox users may have ben exposed to malware not detected by avast. I picked this up in my Firefox cache:
(The malware was still infecting the Google cache of the forum as of yesterday evening.)
Antivirus Version Last Update Result
AhnLab-V3 2007.8.25.0 2007.08.24 -
AntiVir 7.4.1.63 2007.08.25 HTML/Shellcode.Gen
Authentium 4.93.8 2007.08.25 -
Avast 4.7.1029.0 2007.08.25 -
AVG 7.5.0.484 2007.08.25 -
BitDefender 7.2 2007.08.26 -
CAT-QuickHeal 9.00 2007.08.25 -
ClamAV 0.91 2007.08.26 -
DrWeb 4.33 2007.08.26 VBS.Psyme.443
eSafe 7.0.15.0 2007.08.23 -
eTrust-Vet 31.1.5085 2007.08.24 -
Ewido 4.0 2007.08.25 Downloader.Psyme.kt
FileAdvisor 1 2007.08.26 -
Fortinet 2.91.0.0 2007.08.26 VBS/Agent.U!tr.dldr
F-Prot 4.3.2.48 2007.08.25 -
F-Secure 6.70.13030.0 2007.08.24 -
Ikarus T3.1.1.12 2007.08.26 -
Kaspersky 4.0.2.24 2007.08.26 -
McAfee 5105 2007.08.24 -
Microsoft 1.2803 2007.08.26 -
NOD32v2 2484 2007.08.25 -
Norman 5.80.02 2007.08.24 -
Panda 9.0.0.4 2007.08.25 -
Prevx1 V2 2007.08.26 -
Rising 19.37.61.00 2007.08.26 -
Sophos 4.21.0 2007.08.25 Mal/JSShell-C
Sunbelt 2.2.907.0 2007.08.25 -
Symantec 10 2007.08.26 -
TheHacker 6.1.8.173 2007.08.26 -
VBA32 3.12.2.3 2007.08.26 -
VirusBuster 4.3.26:9 2007.08.25 -
Webwasher-Gateway 6.0.1 2007.08.26 Script.Shellcode.Gen
Seems to be an exploit so users of up-to-date Firefox were not at risk.
Still, a scan with Ewido/CureIT! might be in order.
EDIT: The write-up for this malware only states: 'Exploits system or software vulnerabilities', so I'm not sure if it was specifically aimed at Firefox. If it's a VBS as DrWeb and Fortinet suggest, it might also have been aimed at IE. Don't know why I found this one and not the ANI exploit.
http://www.sophos.com/security/analyses/maljsshellc.html