WebKit contains a use-after-free error in the 'ProcessingInstruction::removedFrom' function [WebCore/dom/ProcessingInstruction.cpp]. The issue is triggered when a ProcessingInstruction is removed from the document as the owner is removed, but the style resolver may not be updated. With a specially crafted web page, a context-dependent attacker can dereference already freed memory and potentially execute arbitrary code.
Loss of Integrity
It has been reported that this issue has been fixed. Upgrade to version 1.10.0, or higher, to address this vulnerability. An upgrade is required as there are no known workarounds.
Upgrade to Google Chrome version 21.0.1180.57 or higher for Mac and Linux or 21.0.1180.60 or higher for Windows and Chrome Frame, as they have been reported to fix this vulnerability.