moxieplayer.as in Moxiecode moxieplayer, as used in the TinyMCE Media plugin in WordPress before 3.5.2 and other products, does not consider the presence of a # (pound sign) character during extraction of the QUERY_STRING, which allows remote attackers to pass arbitrary parameters to a Flash application, and conduct content-spoofing attacks, via a crafted string after a ? (question mark) character.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.