Security researcher regenrecht reported via TippingPoint's Zero Day
Initiative that code used to normalize a document contained a logical flaw
that could be leveraged to run arbitrary code. When the normalization code
ran, a static count of the document's child nodes was used in the
traversal, so a page could be constructed that would remove DOM nodes
during this normalization which could lead to the accessing of a deleted
object and potentially the execution of attacker-controlled memory.