We are tracking a few sites that are currently blacklisted and showing a warning from Google that openx.org (home of a popular open source ad server) is the site responsible for the infection:

2 domain(s) appear to be functioning as intermediaries for distributing malware to visitors of this site, including openx.org/.

By looking at the diagnostic page for openx.org itself, it shows:

Has this site acted as an intermediary resulting in further distribution of malware?

Over the past 90 days, openx.org appeared to function as an intermediary for the infection of 82 site(s) including solovenezolanas.com/, thelocal.de/, drtuber.com/.

We are still tracking to see which ads are causing the issue, or if the openx servers themselves are compromised. If you include the tracking code from openx.org, we recommend that you check to see if there isn’t any malicious code being pushed to your users.