Microsoft plugs 26 security holes

The company also warned customers of a new zero-day attack and quashed yet another instance of a bug that the Duqu intelligence-gathering Trojan leveraged.

The software maker also ditched one security update at the last minute and substituted another in its place, probably because the second was more serious.

Of Tuesday's seven security updates, three were rated "critical," Microsoft's top-most threat ranking, while the other four were marked "important," the next-most-serious label.

The 26 vulnerabilities -- one more than Microsoft last week told users to expect -- included 10 critical, 14 important and two judged "moderate" in the company's four-step scoring system.