In 2011, the company issued a Dec. 28 security advisory about a flaw in its ASP .Net programming language that hackers could use to cripple website servers. On Dec. 29, 2011, Microsoft released an "out-of-band," or emergency, update.
Microsoft reminded customers that IE9 and IE10 do not contain the vulnerable code, and are safe to use. Windows XP users, however, cannot use either of those browsers, as Microsoft has limited IE9 to Vista and Windows 7, and IE10 to Windows 7 and Windows 8.
Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed. His email address is firstname.lastname@example.org.
Read more about malware and vulnerabilities in Computerworld's Malware and Vulnerabilities Topic Center.