Microsoft Corp. released an emergency software fix for Internet Explorer on Tuesday after hackers exploited a security flaw in the popular Web browser to attack an unknown number of users. The software maker said on its website it released the software, known as a “Fix It,” as an emergency measure to protect customers after learning about “extremely limited, targeted attacks” that made use of the newly discovered bug. Microsoft said the attacks took advantage of an undiscovered flaw, or “zero day” vulnerability in industry parlance. …