Wordpress4.9.3に不具合、自動アップデートでトラブル、4.９.４がリリース(wasVersion 4.9.4 « WordPress Codex
（情報元のブックマーク数 
Wordpress4.9.3に自動アップデートされていたら壊れるという不具合、4年前に自動アップデートを導入して初トラブルらしい。
とりあえず、4.9.3->4.9.4がリリースされているので、そちらを適用してくださいとのこと。
From the WordPress 4.9.4 release post: This maintenance release fixes a severe bug in 4.9.3, which will cause sites that support automatic background updates to fail to update automatically, and will require action from you (or your host) for it to be updated to 4.9.4.
WordPress 4.9.4 contains 1 bug fix.
Version 4.9.4 « WordPress Codex
From the WordPress 4.9.3 release post: This maintenance release fixes 34 bugs in 4.9, including fixes for Customizer changesets, widgets, visual editor, and PHP 7.2 compatibility.
WordPress 4.9.3 contains 34 bug fixes.
Canonical URLs
#15397 - Redirect to the correct URL when the post date changes.
Code Editor#42802 - Disable attr-value-double-quotes HTMLHint rule since too strict for user input.
#42586 - Add Ctrl/Cmd+F as aliases for persistent search for more intuitive behaviour.
#42850 - Replaces JSHint with esprima.
Customize#42497 - Improve accuracy of message displayed when accessing Customizer with a changeset that is already published or trashed.
#42674 - Prevent showing SFTP theme installation notification in multisite when user cannot install themes.
#42655 - Use changeset-specific "locked" messages when branching is enabled.
#42975 - Prevent frontend previewing from causing a customization lock on the changeset.
#42686 - Let default status for Customizer be draft if user does not have capability to publish.
#42565 - Correct "Add Items" button reference in help text shown after creating a new menu.
#42450 - Ensure customize_autosaved requests only use revision of logged-in user.
#42991 - Include nav menu item for Home custom link in search results for "Home".
#42495 - Ensure media playlists get initialized after selective refresh; expose new wp.playlist.initialize() API.
#42658 - Ensure heartbeat keeps changeset locked when in branching mode.#42693 - Don't send notifications for site or network admin email address change to the default 'admin_email' value.
Emoji#42862 - Update Twemoji to 2.4.0.
#42862 - Update emoji base URL in _print_emoji_detection_script() and wp_staticize_emoji().
Media#43088 - Restore white background of the content area in media modal.
#42643 - Introduce a custom error handler for MediaElement.js to display a download link if a FLV file cannot be rendered for any reason.
#42646 - Store and reuse image cropper ratio settings if available, instead of overwriting.
#42646 - Fix JSHint error after #42595.
#39859 - Avoid page scrolling when opening the media modal.
Plugins#43016 - Update review filter links in Details modal.
REST API#42597 - Add existing term_id to the error data object when attempting to create a duplicate term.
Role/Capability#42697 - Make install_languages capability check less restrictive.
TinyMCE#43090 - On the toolbar drop-downs apply overflow style on the actual element with text.
#42908 - When keeping the scroll position treat all shortcodes as preview-able.
#42722 - Backport bug fixes to NotificationManager, WindowManager and MultiRange.
Upgrade/Install#43005 - In postMessage events handler, check for message object existence before checking its action property.
#43103 - Only trigger Background Update processes from within the core update check when a core autoupdate is on offer.
Widget#43003 - Prevent checkValidity from running on a form when widget is first adding to sidebar.
#42740 - Allow relative/partial URLs in Image Widget's link field.
#43125 - Ensure media is explicitly enqueued from Text widget in case Media widgets are unregistered.
WPDB#43109 - Use a PCRE syntax which supports PCRE compiled between 2003 and 2006.
Version 4.9.3 « WordPress Codex
This maintenance release fixes 34 bugs in 4.9, including fixes for Customizer changesets, widgets, visual editor, and PHP 7.2 compatibility. For a full list of changes, consult the list of tickets and the changelog.
WordPress 4.9.3 Maintenance Release
This maintenance release fixes a severe bug in 4.9.3, which will cause sites that support automatic background updates to fail to update automatically, and will require action from you (or your host) for it to be updated to 4.9.4.
WordPress 4.9.4 Maintenance Release
【追記 2018/2/7】WP4.9.3で壊れた…
この追記時点において、WordPress 3.7以降で自動アップデートが働かなくなってしまったバージョンが唯一存在している。WordPress 4.9.3だ。(#43103で誤って無効化されてしまった)もし、自動アップデートで4.9.3になっている場合、手動アップデートが必要なので注意。4.9.3リリース翌日に4.9.4はリリース済み。(手動といっても管理画面1クリックで問題ない。)
WordPressの自動アップデートが働いていない場合 | ぴんくいろにっき
