Microsoft has released three patches to cover flaws in its operating systems and other software.
The vulnerabilities include a hole in Internet Explorer 7 that could allow a hacker to take control of your PC remotely.
This particular flaw lies in the way that Windows deals with Uniform Resource Identifier (URI) codes, which are used to identify certain bits of content on the web such as an image or video clip.
One of the most common types of URI is a webpage address, or Uniform Resource Locator (URL).
"A remote code execution vulnerability exists in the way that the Windows shell handles specially crafted URIs that are passed to it. If the Windows shell did not sufficiently validate these URIs, an attacker could exploit this vulnerability and execute arbitrary code," a Microsoft statement said.
Security experts highlighted the importance of downloading and installing these patches as soon as possible, or making sure Automatic Updates are enabled on your PC.
"It doesn't take a rocket scientist to realise that it's critical for businesses and home users to have the latest security patches in place. Leaving your computers unpatched means that you are risking becoming the victim of a hacker attack," said Graham Cluley of Sophos.
www.microsoft.com/security www.sophos.com