The fix was scheduled to be released on 10 April - the next date for Microsoft's regular monthly security update.

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Microsoft said the security problem introduced by its update would affect the relatively small number of users running Windows 2000.

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The statistics in the report were gathered from the 600 million machines that are enrolled in Microsoft's various update services or use its Essentials and Defender security packages.

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"Four days is typically not enough to complete the initial investigation of the vulnerability and thoroughly test a comprehensive update, " said Mike Reavey, director of Microsoft's security response center.

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