Smart Defrag

What's new in this version:

Security updates included in this release:
- The security team would like to thank the following people for responsibly reporting vulnerabilities, and allowing them to be fixed in this release.
- Stored XSS via wp-mail.php (post by email) – Toshitsugu Yoneyama of Mitsui Bussan Secure Directions, Inc. via JPCERT
- Open redirect in `wp_nonce_ays` – devrayn
- Sender’s email address is exposed in wp-mail.php – Toshitsugu Yoneyama of Mitsui Bussan Secure Directions, Inc. via JPCERT
- Media Library – Reflected XSS via SQLi – Ben Bidner from the WordPress security team and Marc Montpas from Automattic independently discovered this issue
- CSRF in wp-trackback.php – Simon Scannell
- Stored XSS via the Customizer – Alex Concha from the WordPress security team
- Revert shared user instances introduced in 50790 – Alex Concha and Ben Bidner from the WordPress security team
- Stored XSS in WordPress Core via Comment Editing – Third-party security audit and Alex Concha from the WordPress security team
- Data exposure via the REST Terms/Tags Endpoint – Than Taintor
- Content from multipart emails leaked – Thomas Kräftner
- SQL Injection due to improper sanitization in `WP_Date_Query` – Michael Mazzolini
- RSS Widget: Stored XSS issue – Third-party security audit
- Stored XSS in the search block – Alex Concha of the WP Security team
- Feature Image Block: XSS issue – Third-party security audit
- RSS Block: Stored XSS issue – Third-party security audit
- Fix widget block XSS – Third-party security audit