Windows Versions Have Security Flaw

Microsoft Corp. said all versions of its Windows operating system released since 1996 and its word-processing and Web-viewing software for Apple Computer Inc.’s Macintosh computers have a security flaw that could let a hacker steal passwords or credit cards.

The world’s largest software maker called the weakness “critical,” its most serious of three ratings, in a security bulletin.

A software patch to fix the vulnerability is available for some versions of Windows, and Microsoft urged users to download it immediately from www.microsoft.com.

The error affects products beginning with the Windows NT 4.0 server program that went on sale in July 1996. The earliest PC version with the flaw is Windows 98, released in June 1998. Windows 2000 and Windows XP, the most recent versions of the operating system, also are affected.