As noted on WordPress.org:
WordPress 5.4.2 is now available!
This security and maintenance release features 23 fixes and enhancements. Plus, it adds a number of security fixes—see the list below.
These bugs affect WordPress versions 5.4.1 and earlier; version 5.4.2 fixes them, so you’ll want to upgrade.
If you haven’t yet updated to 5.4, there are also updated versions of 5.3 and earlier that fix the bugs for you.
WordPress versions 5.4 and earlier are affected by the following bugs, which are fixed in version 5.4.2. If you haven’t yet updated to 5.4, there are also updated versions of 5.3 and earlier that fix the security issues.
- Props to Ben Bidner of the WordPress Security Team for finding an open redirect issue in wp_validate_redirect().
- Props to Nrimo Ing Pandum for finding an authenticated XSS issue via theme uploads.
- Props to Simon Scannell of RIPS Technologies for finding an issue where set-screen-option can be misused by plugins leading to privilege escalation.
- Props to Carolina Nymark for discovering an issue where comments from password-protected posts and pages could be displayed under certain conditions.
Thank you to all of the reporters for privately disclosing the vulnerabilities. This gave the security team time to fix the vulnerabilities before WordPress sites could be attacked.
One maintenance update was also deployed to versions 5.1, 5.2 and 5.3. See the related developer note for more information.
You can browse the full list of changes on Trac.
For more info, browse the full list of changes on Trac or check out the Version 5.4.2 documentation page.
WordPress 5.4.2 is a short-cycle maintenance release. The next major release will be version 5.5.
You can download WordPress 5.4.2 from the button at the top of this page, or visit your Dashboard → Updates and click Update Now.
If you have sites that support automatic background updates, they’ve already started the update process.