WebKit in Apple Safari before 5.0 on Mac OS X 10.5 through 10.6 and Windows, and before 4.1 on Mac OS X 10.4, does not properly handle libxml contexts, allows remote attackers to execute arbitrary code or cause a denial of service (application crash) via a crafted HTML document, related to an "API abuse issue."
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.