If you are still using Internet Explorer, the U.S. Department of Homeland Security is urging you to stop doing so immediately. The warning comes after a fatal security flaw in the web browser was discovered over the weekend.

On Saturday, FireEye first reported on the attack, which affects versions of IE 9 through 11, although it was later reported that it affects versions as far back as IE6. Microsoft later said that it is working to find some kind of solution for the problem.

In the meantime, FireEye suggests that IE users shut off Adobe Flash, which the attackers can use to hit a computer’s memory. According to USA Today, the blog noted that the hackers are exploiting this bug in Adobe Flash to access the victims’ computers. A victim is lured to download a Flash file, which will then allow the attacker access to the victims’ IE browser and their computer.

Homeland Security must believe that this is just a temporary fix to the issue and has since issued a warning to all Americans still using IE. “We are currently unaware of a practical solution to this problem,” the agency said, offering several options to get around the issue.

Unfortunately, when Microsoft comes up with a fix, it will not be able to help Windows XP users, since the company stopped supporting that system on April 8.