Hackers have discovered a new vulnerability in Internet Explorer, and they’ve released code that could be used to attack users of Microsoft Corp.’s popular browser. To take advantage of the exploit code, attackers would first need to trick users into viewing a maliciously encoded Web page, but they could then run unauthorized code on a victim’s computer. Symantec calls the bug “critical,” and Secunia rates the issue as “highly critical,” its most severe rating.