Adobe did not respond to questions today about how it will work with Google and Mozilla, or whether it will.

And neither Google or Mozilla immediately replied to questions about how they plan to compete with the Flash-equipped IE10. Both firms have pledged to come up with Metro versions of their Chrome and Firefox browsers, and last month each had dunned their rival's decision to (application programming interfaces) from within Metro.

Because Microsoft has baked Flash Player into IE10, it will also use its own Windows Update service to provide security and feature updates to Adobe's software. Previously, Chrome was the only browser that included Flash Player updates with its browser.

"By updating Flash through Windows Update, like IE, we make security more convenient for customers," said Hachamovitch.

But not all websites with Flash will be viewable using IE10 on Metro, Hachamovitch warned: Only those sites that Microsoft adds to IE's Compatibility View (CV) list -- a whitelist that debuted in 2011 with IE8, designed to allow URLs to render as if they were viewed by an older version of the browser -- will show Flash in Metro's IE10.