Impact

WordPress users with lower privileges (like contributors) can inject JavaScript code in the block editor using a specific payload, which is executed within the dashboard. This can lead to XSS if an admin opens the post in the editor. Execution of this attack does require an authenticated user.

Patches

This has been patched in WordPress 5.3.1, along with all the previous affected WordPress versions via a minor release. Automatic updates are enabled by default for minor releases and we strongly recommend that you keep them enabled.

References

• https://wordpress.org/news/2019/12/wordpress-5-3-1-security-and-maintenance-release/
• https://hackerone.com/reports/738644

For more information

If you have any questions or comments about this advisory:

• Open an issue on HackerOne