I received a report from Google that one of my sites was infected with malware. I looked into it further and found that nearly all my domains have been infected. I used this tool from Sucuri to verify the malware: http://sitecheck.sucuri.net/scanner/
I am hosting 8 domains, and 7 are infected. They all have WordPress. I first thought it was isolated to a certain theme, but my 7 sites use different themes from different developers, and they have all been infected.
A few domains were out of date, but even brand new domains that I created earlier this month with the latest WP and theme versions have been infected.
Now 1 domain was not infected and the only difference I could find was I did not install this Quick Cache plugin. All other 7 domains have Quick Cache.
Has anyone else ran into malware isseus? Try running the scanner tool above on your WP hosted domain.