CVE-2022-4973 - Exploiting Stored XSS in WordPress Core up to 6..2 via `the_meta()`—A Simple Breakdown

WordPress is the world’s most popular content management system, powering over 40% of all websites. With a userbase that massive, any vulnerability in the WordPress core can affect millions. One such recent vulnerability is CVE-2022-4973, a security flaw discovered in WordPress Core, versions up to 6..2. This vulnerability allows authenticated users to inject malicious scripts into posts or pages, which are executed when the_meta(); function is used in a template.

In this post, let's break down—in straightforward, everyday language—how this vulnerability works, who it affects, how it can be exploited, and how you can protect yourself, including some practical code snippets and references.

1. What Is CVE-2022-4973?

CVE-2022-4973 is an Authenticated Stored Cross-Site Scripting (XSS) vulnerability in WordPress core. This means that, if you are logged in with "Author", "Editor", or even "Contributor" rights, you could inject JavaScript or other dangerous code that is saved (stored) in the database and later run when someone visits a page using the the_meta() template function.

Example of the at-risk function

<?php 
if ( function_exists('the_meta') ) {
    the_meta();
}
?>

Every time this code runs in your theme—and there are custom fields that include user input—any malicious scripts stored there could execute in a viewer's browser.

This does *not* require admin rights.

- Attackers must be logged in, but on many WordPress sites, giving these roles is common (guest posting, multi-author blogs, etc).

3. How Does the Exploit Work?

In short:

- Add a custom field named, e.g., dangerous, with value

"><script>alert('XSS by CVE-2022-4973!');</script>

c) Victim View

Any user visiting a template displaying metadata via the_meta(); will trigger the payload.

Example Code in the Template:

<!-- Theme's single post template example -->
<div class="post-meta">
    <?php the_meta(); ?>
</div>

What Happens Next?

The script is rendered as part of the page, causing JavaScript code (like an alert, or a more malicious script) to execute within the visitor's browser.

`html

">

6. How Was It Patched?

WordPress core sanitized custom field output in the_meta() after version 6..2. Now, special characters and HTML tags are properly escaped, so scripts can’t run. Always update your WordPress version!

7. Official References

- WordPress Security Release for 6..2
- CVE Record: CVE-2022-4973
- WordPress.org Changelog

Update to WordPress 6..3 or later.

- Limit Editor/Author/Contributor access.

Remove or rewrite themes that use the_meta(); if not needed.

- Consider using a security plugin like Wordfence or Sucuri for extra coverage.

9. Alternative Mitigation (If you MUST use Old WordPress)

If for some reason you can’t upgrade yet, you can add the following code to sanitize custom fields output:

function safe_the_meta() {
    $custom_fields = get_post_custom();
    foreach ( $custom_fields as $key => $values ) {
        foreach ( $values as $value ) {
            echo '<li><span>' . esc_html( $key ) . '</span>: ';
            echo esc_html( $value ) . '</li>';
        }
    }
}
add_filter( 'the_meta', 'safe_the_meta' );

*(This will make the_meta safe by escaping output.)*

10. In Summary

- CVE-2022-4973 made it easy for logged-in writers to inject scripts in WordPress sites that weren’t properly escaping custom fields.

Fix: Update WordPress—it’s that simple!

Always keep your WordPress and plugins up to date. It only takes one missing patch to let an attacker take over your site.

Stay safe, and always verify what inputs your website displays!

Timeline

Published on: 10/16/2024 07:15:12 UTC
Last modified on: 10/30/2024 15:58:30 UTC