The published exploit for WordPress 3.0.4 isn’t accurate

We were informed yesterday of a published vulnerability for WordPress 3.0.4, “Stored XSS (via Editor role)”.

This is an invalid report. (Edit: The exploit has been delisted by the database.)

The dead giveaway was the title: “via Editor role.” In WordPress, users with the role of Editor or Administrator have the ability to post unfiltered HTML. It has always been like this.

From the Security FAQ on the Codex:

Users with Administrator or Editor privileges are allowed to publish unfiltered HTML in post titles and content. WordPress is, after all, a publishing tool, and people need to be able to include whatever markup they need to communicate. Users with lesser privileges are not allowed to post unfiltered content.

We also issue a warning for security researchers, which wasn’t followed here:

If you are running security tests against WordPress, use a lesser privileged user so that all content is filtered.

How to change this behavior

In multisite, only super administrators can publish unfiltered HTML. All other users are considered untrusted in this case, as they can be administrators for their own sites. (There is a plugin to restore unfiltered HTML to editors and regular administrators in this case, if you trust those users: Unfiltered MU.)

There’s a constant you can use to disallow unfiltered HTML for everyone, including administrators and super administrators. To disallow unfiltered HTML for all users, you can add this to wp-config.php:

define( 'DISALLOW_UNFILTERED_HTML', true );

Filtered HTML for Editors

To deny unfiltered HTML for Editors, try the Filtered HTML for Editors plugin, which I put together today. The description and FAQ go into much of what was covered here.

How to report security vulnerabilities

Standard practice when finding a security vulnerability is to privately notify the vendor and give them an opportunity to respond and prepare a fix for public release. It’s the concept of responsible disclosure. We’ll always credit responsible disclosure in the release announcement as the person requests, such as with a link to your blog.

For WordPress, suspected vulnerabilities can be privately emailed to our security team at security@wordpress.org.

Unfortunately, not everyone follows responsible disclosure. In the case of 3.0.4, an exploit published regarding 3.0.3 forced our hand to release the fix we had been privately testing (thanks to responsible disclosure). This can sometimes force our hand in very bad ways — the fixes included in 3.0.4 were very complicated and involved more than a hundred hours of work from more than a dozen individuals. Had we rushed a release due to a public announcement, we might have missed something.

Not following responsible disclosure also prevents us from responding to invalid reports. Unfiltered HTML results in false reports every so often. The fact that this was published as an exploit, without any confirmation or notification, only contributes to FUD and perception issues.

The status of WordPress 3.0.4

This all said, there are currently no known vulnerabilities for WordPress 3.0.4. I’ll go knock on wood now.