WordPress Release: 5.5.0

TL;DR

WordPress 5.5 introduces major improvements in speed, search, and security. This release brings automatic updates for plugins and themes, a built-in XML sitemap, lazy-loading images, and significant updates to the block editor. It also includes important accessibility improvements, better control over default taxonomy terms, and numerous bug fixes and performance enhancements that make WordPress faster and more reliable.

Highlight of the Release

• Automatic updates for plugins and themes
• Built-in XML sitemap for better search engine visibility
• Lazy-loading images for improved performance
• Enhanced block editor with block patterns and inline image editing
• Block directory for installing new block types directly from the editor
• Improved accessibility throughout WordPress
• Better control over default taxonomy terms

Migration Guide

Inclusive Language Changes

Several function and variable names have been changed to use more inclusive language. If your code uses any of the following, you should update it:

• $new_whitelist_options is now $new_allowed_options
• add_option_whitelist() is now add_allowed_options()
• remove_option_whitelist() is now remove_allowed_options()

For backward compatibility, the old functions and variables still work but will trigger deprecation notices.

Default Taxonomy Terms

The handling of default terms for custom taxonomies has been adjusted:

• Default term assignment moved from wp_set_object_terms() to wp_insert_post()
• The option key for default terms changed from default_taxonomy_$taxonomy to default_term_$taxonomy

If your code manages default terms for custom taxonomies, you may need to update it.

REST API Permission Callbacks

The REST API now issues a _doing_it_wrong notice when registering a route without a permission callback. If you have custom REST API endpoints, ensure they include a permission callback, even if it's just __return_true for public endpoints.

Block Editor Changes

If your theme or plugin interacts with the block editor:

• Check compatibility with the new block patterns feature
• Test any custom blocks with the new inline image editing capabilities
• If you want to opt out of core block patterns, use remove_theme_support('core-block-patterns')

Custom Logo Changes

Themes that use the custom-logo feature now have the option to control whether the logo should be linked on the home page using the unlink-homepage-logo parameter:

add_theme_support('custom-logo', array(
    'unlink-homepage-logo' => true,
));

Upgrade Recommendations

WordPress 5.5 is a major update with significant improvements to performance, security, and functionality. It is strongly recommended for all WordPress users to upgrade to this version.

Before upgrading:

1. Create a complete backup of your WordPress site, including all files and the database
2. Test on a staging environment if possible, especially if you use custom themes or plugins
3. Update all themes and plugins to their latest versions to ensure compatibility

After upgrading:

1. Test your site thoroughly, checking all critical functionality
2. Review auto-update settings for plugins and themes, enabling them selectively based on your needs
3. Check your XML sitemap at /wp-sitemap.xml to ensure it's working correctly
4. Verify image loading behavior if you have custom image implementations that might be affected by lazy-loading

If you're a developer with custom code that interacts with WordPress core, review the migration guide for changes that might affect your code, particularly around inclusive language changes, default taxonomy terms, and REST API endpoints.

Bug Fixes

Comment Type Standardization

Empty comment types are now standardized to comment in the database, fixing inconsistencies in comment handling and improving compatibility with plugins that rely on comment types.

REST API Request Handling

Fixed issues with the REST API's handling of JSON requests with empty bodies, preventing PHP warnings when using set_param().

Attachment Metadata Preservation

When editing images, metadata such as title, caption, alt text, and description are now properly preserved from the parent image.

Post Status Handling in Revisions

Fixed an issue where the global $post could be unexpectedly modified after restoring a revision.

Custom Logo Linking

Fixed accessibility issues with custom logos by adding proper aria-current attributes and allowing themes to control whether the logo should be linked on the home page.

Email Validation and Sending

Improved email validation by using WordPress's is_email() function for PHPMailer validation, and fixed hostname determination for email sending on various server configurations.

File Name Sanitization

Enhanced sanitize_file_name() to handle special characters and accents more consistently, bringing it in line with other WordPress sanitization functions.

Database Query Improvements

Fixed issues with get_lastpostmodified() for custom post types and improved handling of the child_of argument in get_terms() when used with specific field formats.

New Features

Automatic Updates for Plugins and Themes

WordPress 5.5 introduces the ability to enable automatic updates for plugins and themes directly from the WordPress admin. This feature helps keep sites secure and up-to-date with minimal manual intervention. Site administrators can toggle auto-updates for each plugin and theme individually.

Built-in XML Sitemap

A native XML sitemap feature is now included in WordPress core, making it easier for search engines to discover and index content. The sitemap is automatically generated and accessible at /wp-sitemap.xml, with additional sitemaps for different content types.

Block Patterns

The block editor now includes predefined block patterns that make it easier to create complex layouts. These patterns can be inserted directly into posts and pages, providing a quick way to add professionally designed content sections.

Block Directory Integration

WordPress 5.5 integrates the block directory directly into the editor, allowing users to search for, install, and insert third-party blocks without leaving the editor interface.

Lazy-Loading Images

Images now include the loading="lazy" attribute by default, which defers loading off-screen images until the user scrolls near them. This improves page load performance and reduces bandwidth usage.

Inline Image Editing

The block editor now supports inline image editing capabilities, allowing users to crop, rotate, and zoom images directly within the editor without having to use an external image editor.

Environment Type API

A new API for determining the current environment type (production, staging, development, etc.) has been added, making it easier for plugins and themes to adjust their behavior based on the environment.

Security Updates

PHPMailer Update

WordPress 5.5 updates PHPMailer to version 6.1.6, addressing security vulnerabilities in the previous version and improving email handling.

Root Certificate Bundle Update

The Root Certificate bundle has been updated to include the latest certificates while maintaining compatibility with older OpenSSL versions.

Improved Plugin and Theme Installation

Enhanced security checks for plugin and theme installations, including verification of PHP and WordPress version requirements when uploading from ZIP files.

Accessibility Improvements for Auto-Updates

The accessible audible messages for plugin and theme auto-updates have been improved, with error messages now using the assertive politeness level for better screen reader support.

Performance Improvements

Lazy-Loading Images

All images in WordPress now include the loading="lazy" attribute by default, which significantly improves page load performance by deferring the loading of off-screen images until the user scrolls near them. This reduces initial page load time and bandwidth usage.

REST API Context Filtering

The performance of rest_filter_response_by_context() has been optimized by eliminating repetitive comparisons and loops, improving the handling of REST API responses.

OPcache Invalidation

The wp_opcache_invalidate() function now uses substr() instead of preg_match() for checking file extensions, resulting in better performance when clearing the OPcache during updates.

Database Upgrade Handling

WordPress now avoids triggering database upgrades during Ajax requests via wp-admin/async-upload.php, preventing unnecessary database operations during media uploads.

Impact Summary

WordPress 5.5 represents a significant step forward in the platform's evolution with its focus on speed, search, and security. The introduction of automatic updates for plugins and themes addresses one of the most common security vulnerabilities in WordPress sites - outdated components. This feature alone will help millions of sites stay more secure with minimal effort from site administrators.

The built-in XML sitemap feature is a game-changer for search engine optimization, eliminating the need for additional plugins to handle this critical functionality. Combined with the performance improvements from lazy-loading images, WordPress sites will now be faster and more discoverable by default.

For content creators, the block editor continues to mature with powerful new features like block patterns, inline image editing, and the block directory integration. These improvements make creating rich, well-designed content more accessible to users of all skill levels.

Developers benefit from numerous API improvements, better standardization of core functionality, and more consistent behavior across the platform. The environment type API and metadata handling enhancements provide more robust tools for building sophisticated WordPress applications.

The focus on accessibility throughout this release ensures that WordPress continues to be usable by people of all abilities, reinforcing its position as an inclusive publishing platform.

Overall, WordPress 5.5 delivers meaningful improvements that benefit all types of users while maintaining backward compatibility and the flexibility that has made WordPress the world's most popular CMS.