Microsoft published today a large Security Update for Internet Explorer. This happens nearly every month, but this time, this is really important. Whatever your version of Internet Explorer, you should upgrade now, via Windows Update.
Microsoft is correcting a major bug in all versions of Internet Explorer and it is urgently important that you plug this security hole that could leave your computer totally open to external hackers.
Nota bene: generally speaking, you should try and keep your computer up-to-date for security issues. You may want tot check my previous post about Secunia PSI.