According to AllThingsD, the site was likely hijacked by a malware scammer trying to bait users into installing fake anti-virus software. To its credit, the Times quickly posted a warning on its site.
MediaMemo reader Tim Minter told AllThingsD:
The ad hijacked my computer. Say I’m reading an article (the Clean Water Act was the one that caught me). It then redirects my browser involuntarily to sex-and-the-city.cn. That site then redirects to the ad I screen-captured. At no time did I click anything. That’s what is so nefarious about this malware. Thankfully, since I run OS X, I knew immediately it was malware (seeing Windows XP on a Mac where that’s not installed is suspicious).
The warning from the Times:
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 firstname.lastname@example.org.