XSS en WordPress 4.2

Solo han tardado unos días en encontrar una vulnerabilidad en la nueva versión de WordPress. Hace un rato lo soltaban en securityfocus. Es de esperar el parche en breve … mientras tanto ojo con los comentarios.

El documento con los datos se puede consultar http://klikki.fi/adv/wordpress2.html

Y estos son los detalles del mismo:


Current versions of WordPress are vulnerable to a stored XSS. An unauthenticated attacker can inject JavaScript in WordPress comments. The script is triggered when the comment is viewed.

If triggered by a logged-in administrator, under default settings the attacker can leverage the vulnerability to execute arbitrary code on the server via the plugin and theme editors.

Alternatively the attacker could change the administrator’s password, create new administrator accounts, or do whatever else the currently logged-in administrator can do on the target system.


If the comment text is long enough, it will be truncated when inserted in the database. The MySQL TEXT type size limit is 64 kilobytes so the comment has to be quite long.

The truncation results in malformed HTML generated on the page. The attacker can supply any attributes in the allowed HTML tags, in the same way as with the two other recently published stored XSS vulnerabilities affecting the WordPress core.

The vulnerability bears a similarity to the one reported by Cedric Van Bockhaven in 2014 (patched this week, after 14 months). Instead of using an invalid UTF-8 character to truncate the comment, this time an excessively long comment text is used for the same effect.

In these two cases the injected JavaScript apparently can’t be triggered in the administrative Dashboard, so these exploits require getting around comment moderation e.g. by posting one harmless comment first.

Lo dicho… hasta que haya parche ojo con los comentarios …