Microsoft has released update KB2799329 to patch a security vulnerability found in Internet Explorer 8, 7 and 6 that could allow hackers to take control of a Windows-based computer if the user visits a malicious website. Microsoft released a quick fix, but there wasn't a permanent patch solution available just yet.
If you have automatic updating enabled, then the patch will be installed automatically. Internet Explorer 9 and 10 are more resistant to security attacks. If possible, you should upgrade to Windows 7 or Windows 8, since IE9 can't be installed on Windows XP.
Or as Avast suggested, switch to more secure browser like Chrome if you are still using Windows XP.