CRLF injection vulnerability in WebKit in Apple Safari before 4.0, iPhone OS 1.0 through 2.2.1, and iPhone OS for iPod touch 1.1 through 2.2.1 allows remote attackers to inject HTTP headers and bypass the Same Origin Policy via a crafted HTML document, related to cross-site scripting (XSS) attacks that depend on communication with arbitrary web sites on the same server through use of XMLHttpRequest without a Host header.