Advisory by Jose Carlos Norte

Wordpress is vulnerable to XSS attacks when custom 404 pages are used by the template.

The problem (sidebar.php):

<form method="get" id="searchform" action="<?php echo $_SERVER['PHP_SELF']; ?>">

if wordpress template use custom 404 pages, like:

<?php get_header(); ?>

<div id="content" class="narrowcolumn">

<h2 class="center">Error 404 - Not Found</h2>

</div>

<?php get_sidebar(); ?>

$_SERVER['PHP_SELF']; can contain special characters to break out html and perform XSS attacks, example:

http://www.example.com/index.php/"><script>alert(document.cookie)</scrip
t>

if no custom 404 page set by wordpress theme this attacks is not posible.

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