Microsoft Internet Explorer 7 for Windows XP SP2 and SP3; 7 for Server 2003 SP2; 7 for Vista Gold, SP1, and SP2; and 7 for Server 2008 SP2 allows remote attackers to execute arbitrary code via frequent calls to the getElementsByTagName function combined with the creation of an object during reordering of elements, followed by an onreadystatechange event, which triggers an access of an object that (1) was not properly initialized or (2) is deleted, aka "HTML Object Memory Corruption Vulnerability."