FireEye (FEYE), the security company which identified the flaw, said hackers are focusing on versions 9 through 11, which puts around 26% of global browser users in jeopardy.
The nature of the threat, however, means users won't instantly be compromised simply by using the browser. Users would have to click on an attacker's website or access malicious links.
In a statement, Microsoft explains, "An attacker would have no way to force users to visit these websites. Instead, an attacker would have to convince users to visit the website, typically by getting them to click a link in an email message or Instant Messenger message that takes users to the attacker's website."
Once in though, hackers could remotely install viruses or even harvest private information.
Microsoft said it plans to issue a patch once it finishes investigating the issue. In the meantime, FireEye recommends using Internet Explorer's enhanced protection settings or to disable Adobe Flash plugins.
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