By Tech Editor Ian Bush

PHILADELPHIA (CBS) — It only takes one click …

Microsoft is warning of a security flaw in its Internet Explorer web browser that has left millions of PCs vulnerable to attack.

It’s so serious, the German government has joined computer experts here in the U.S. in urging people to stop using Internet Explorer until the hole is fixed.

For now, there’s no patch for the bug. Malicious web site operators need only convince you to click a legit-looking link in an e-mail or search before they can take over control of your computer.

Microsoft says there has been a very small number of attacks; security firms expect the virus is targeting bigger fish.

But that doesn’t mean your machine can’t be compromised.

To protect yourself, use another free browser like Chrome or Firefox.

Microsoft suggests switching Internet security settings to “high,” though that may affect your browsing experience.

There’s also a tool that beefs up Internet Explorer’s protections at http://support.microsoft.com/kb/2458544.

More on the security flaw: http://technet.microsoft.com/en-us/security/advisory/2757760.

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