On Saturday, Microsoft published a security advisory warning users of Internet Explorer 6, 7, and 8 that they could be vulnerable to remote code execution hacks. The company said that users of IE 9 and 10 were not susceptible to similar attacks and recommended that anyone using the older browsers upgrade. Still, customers who still run Windows XP can not upgrade to IE 9 and 10 without upgrading their OS.

Microsoft's confirmation comes after reports from several security groups that the attack sprung from the Council of Foreign Relations website, creating a “watering hole attack” that left people who visited the site through older versions of the browser open to further attack.

The company has released a workaround for the problem, and said that it is working on a patch for IE 6, 7, and 8, but did not give a time period as to when those patches would be released. The Council of Foreign Relations told The Washington Free Beacon that it was investigating the situation and working to prevent security breaches like this down the line.

According to The Next Web, the CFR website was compromised with JavaScript that served malicious code to older IE browsers whose language was set to “English (US), Chinese (China), Chinese (Taiwan), Japanese, Korean, or Russian.” The code then created a heap-spray attack using Adobe Flash Player.

While some reports claim that the attack was traced to Chinese hackers, this is unconfirmed. Computerworld describes the hack as highly targeted, however: “In a watering hole campaign, hackers identify their intended targets, even to the individual level, then scout out which websites they frequently visit. Attackers next compromise one or more of those sites, plant malware on them, and like a lion waits at a watering hole for unwary wildebeests, wait for unsuspecting users to surf there.”

Computerworld also points out that this vulnerability is similar in timing to a vulnerability that occurred December 28 last year, which Ars reported as having compromised a long list of technologies, including Microsoft's ASP.NET. Microsoft then published a workaround for ASP.NET website admins in the wake of the discovery of the exploit.