They're saying some of the mods for Fallout 4 were altered and a .dll file inserted into a few of them a few days ago, but from what I'm seeing it could well be some dodgy malware in their site ads.
Anyway, check for the dsound.dll file if you downloaded any mod from Nexus recently, and if you're affected best to secure your accounts if you re-use passwords (advice: don't ever re-use passwords and don't use emails for throwaway sign up sites for your serious/financial affairs as well). Also if on firefox use NoScript to block unwanted javascript.
http://www.nexusmods.com/fallout4/news/12670/?page=6&sort=DESC&pid=0&thread_id=3508890&pUp=1.