Microsoft released an unprecedented number of software security updates to plug flaws in its products, including seven “critical” defects that it said hackers could use to hijack vulnerable computers running the Windows operating system.

Microsoft rated seven of the flaws critical, its most dire warning, saying that the holes could allow attackers to take control of affected PCs just by convincing users to visit certain Web sites. Three of the flaws reside on the company’s Internet Explorer Web browser.

You can download the updates using windows update or by visiting microsoft’s security center