A new series of mass-injections have been targeting WordPress sites as of late and appear to have already infected more than 200,000 web pages. The injections lead unsuspecting users to a bogus AV site that appears to perform a scan on the computer, allegedly as part of a Windows Security Alert The graphic that pops on screen resembles a Windows Explorer window that after running the scan encourages the user to download an anti-virus program that turns out to be a Trojan.
Source: https://threatpost.com/fake-antivirus-lives-now-infecting-200k-wordpress-sites-030712/76295/