CVE 2009-1699
The XSL stylesheet implementation 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 does not properly handle XML external entities, which allows remote attackers to read arbitrary files via a crafted DTD, as demonstrated by a file:///etc/passwd URL in an entity declaration, related to an "XXE attack."
See the 
CVE page on Mitre.org
for more details.
