According Barracuda Labs report, the attack doesn't involve any ad network. It means attackers managed to compromise the main website itself.
The visitors to website are redirected to a page hosting exploit pack that take advantage of vulnerability in the visitors' system to serve malicious software.
The threat is only detected by 8 out of 48 Antivirus engine in Virustotal, most of top Internet security solutions fail to detect it.
It is unknown whether the problem is fixed or not. So, users are advised to avoid visiting the cracked website until the issue is addressed.