The United States Department of Homeland Security is warning Americans to not use Internet Explorer, until a fix is found and disseminated for a major security flaw that was discovered by the security firm, FireEye. One assumes that other nationalities should be wary as well.
I will go further and state that you should never use Internet Explorer at all. Part of the reason for this is that since Internet Explorer is based on proprietary, secret software, no one really knows what is going on in the product. In this situation, as in others, Microsoft has known about the flaw and said nothing until the flaw was found and publicized by FireEye. No one knows how long they have known and what they are doing about it.