The HTMLMediaElement::loadResource function in html/HTMLMediaElement.cpp in WebCore in WebKit before r49480, as used in Apple Safari before 4.0.4 on Mac OS X, does not perform the expected callbacks for HTML 5 media elements that have external URLs for media resources, which allows remote attackers to trigger sub-resource requests to arbitrary web sites via a crafted HTML document, as demonstrated by an HTML e-mail message that uses a media element for X-Confirm-Reading-To functionality, aka rdar problem 7271202.