Oops. The New York Times reports on itself:

Some NYTimes.com readers have seen a pop-up box warning them about a virus and directing them to a site that claims to offer antivirus software. We believe this was generated by an unauthorized advertisement and are working to prevent the problem from recurring. If you see such a warning, we suggest that you not click on it. Instead, quit and restart your Web browser. Questions and comments can be sent to [email protected].

Just to be safe, don’t click on any ads on NYTimes.com until they can explain how an “unauthorized advertisement” ended up on their site.