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What Each Rule Means

Updated October 30, 2026 6 min read

Every finding is produced by one rule. This article lists all 14 rules in version 1.0.0, grouped by the change they cover. The detail page for a plugin shows the same Why it matters and How to fix text and links to the official developer note.

Iframed editor (WordPress 7.1)#

Editor script queries the canvas through the global document#

  • Severity: High. Confidence: High. Runs on: editor scripts only.
  • What it finds: document.querySelector(…), querySelectorAll or getElementsByClassName calls whose selector targets canvas elements (.editor-styles-wrapper, .is-root-container, .block-editor-block-list__layout, .block-editor-block-list__block, .block-editor-writing-flow, .wp-block…).
  • Why it matters: Since 7.1 the post editor canvas is always an iframe. The global document is the admin page, so this selector returns nothing or the wrong elements.
  • Fix: Get the canvas document from an element inside it (element.ownerDocument / defaultView), or use useRefEffect on a block ref.

Editor script uses jQuery on canvas elements without the iframe document#

  • Severity: High. Confidence: High. Runs on: editor scripts only.
  • What it finds: Single-argument jQuery('…') or $('…') calls whose selector targets canvas elements.
  • Why it matters: A single-argument jQuery call searches the admin page, not the editor iframe, so nothing is found.
  • Fix: Pass the canvas document as the context, $( '.wp-block', canvasDocument ), or drop jQuery and use a block ref.

Editor stylesheet only reaches the canvas through the deprecated compatibility copy#

  • Severity: Medium. Confidence: High. Runs on: editor stylesheets whose handle does not start with wp-.
  • What it finds: CSS rules with .editor-styles-wrapper or .wp-block… selectors in a stylesheet that is enqueued on enqueue_block_editor_assets, which loads outside the iframe.
  • Why it matters: WordPress 7.1 still copies such stylesheets into the canvas, but logs a console warning; the copy is a back-compat path that will go away.
  • Fix: Enqueue canvas styles on enqueue_block_assets (inside is_admin()), via block.json editorStyle / style, or with add_editor_style().

Editor stylesheet never reaches the canvas because its handle starts with wp-#

  • Severity: High. Confidence: High. Runs on: editor stylesheets whose handle starts with wp-.
  • What it finds: The same canvas selectors as the rule above, but in a stylesheet whose handle begins with wp-.
  • Why it matters: WordPress copies editor stylesheets into the canvas only when the handle does not start with wp-, so these rules never apply at all.
  • Fix: Enqueue the stylesheet on enqueue_block_assets or through block.json, and give it a handle that does not start with wp-.

Block registers apiVersion below 3#

  • Severity: Low. Confidence: Medium. Runs on: block.json files (one per block name).
  • What it finds: "apiVersion": 1 or 2, or no apiVersion at all (which defaults to 1; the finding says so).
  • Why it matters: Before 7.1 a single apiVersion 1/2 block kept the post editor out of the iframe. In 7.1 it is iframed anyway, so this block has probably never been tested in an iframe.
  • Fix: Set "apiVersion": 3 and test the block in the iframed editor.

List tables (WordPress 7.1)#

CSS targets the old list-table row markup (th.check-column or td title cells)#

  • Severity: Medium. Confidence: High. Runs on: every CSS file.
  • What it finds: Selectors such as th.check-column, td.column-title, td.page-title, td.column-primary, td .row-title, td .row-actions, td .post-state.
  • Why it matters: In 7.1 WP_List_Table renders the checkbox cell as td.check-column and the primary (title) cell as th scope="row". These selectors no longer match.
  • Fix: Drop the element qualifier (.check-column, .column-title) or use :is(td, th).column-title to support old and new markup.

Script selects the old list-table row markup (th.check-column or td title cells)#

  • Severity: Medium. Confidence: Medium. Runs on: every JS file.
  • What it finds: String selectors in scripts that look for the checkbox in a th or the title in a td, including th input[type=…].
  • Why it matters: Bulk-action and quick-edit scripts that rely on the old markup find nothing on 7.1 list tables.
  • Fix: Select .check-column input and .column-primary without an element qualifier.

Editor components (WordPress 7.1)#

Passes the deprecated size prop to a 40px-default component#

  • Severity: Low. Confidence: Medium. Runs on: script bundles.
  • What it finds: A size prop passed to BorderBoxControl, BorderControl, FontSizePicker or ToggleGroupControl, in JSX or compiled createElement calls.
  • Why it matters: In 7.1 these controls are always 40px and the size prop does nothing, so a control sized for a compact layout renders larger.
  • Fix: Remove the size prop (and any size="__unstable-large"); adjust the surrounding layout if it relied on the smaller size.

Passes __next40pxDefaultSize, which no longer does anything#

  • Severity: Info. Confidence: High. Runs on: script bundles.
  • What it finds: Any use of __next40pxDefaultSize.
  • Why it matters: Since 7.1 all affected controls are 40px tall. The prop is ignored, and passing false no longer gives a 36px control.
  • Fix: Remove the prop. If a layout depended on 36px controls, adjust it.

Meta boxes#

Meta box declares itself incompatible with the block editor#

  • Severity: Medium. Confidence: High. Status: shipped (since WordPress 5.0). Runs on: meta boxes recorded by the runtime check.
  • What it finds: A meta box registered with __block_editor_compatible_meta_box => false (and without __back_compat_meta_box => true). Core meta boxes are ignored.
  • Why it matters: The block editor shows a notice instead of the box’s fields. Editors lose this feature unless they switch to the classic editor.
  • Fix: Ask the vendor for a block editor version (a sidebar panel using post meta registered with show_in_rest), or a newer release that drops the flag.

Classic meta box will turn off real-time collaboration on this post type#

  • Severity: Medium. Confidence: High. Status: upcoming. Runs on: meta boxes recorded by the runtime check.
  • What it finds: Any plugin or theme meta box shown in the block editor that does not pass __rtc_compatible_meta_box => true or __back_compat_meta_box => true. Core meta boxes are ignored. The finding lists every post type the box appears on and the file and line of its render callback.
  • Why it matters: Classic meta boxes are not synced between editors, so collaboration is disabled on any post that shows one.
  • Fix: Move the fields to registered post meta (show_in_rest) with a block editor panel, or, if the box is safe, pass '__rtc_compatible_meta_box' => true in the add_meta_box() callback arguments. That flag is proposed and may change.

React 19 (upcoming)#

Bundles React 18’s jsx-runtime instead of the WordPress external#

  • Severity: High. Confidence: High. Status: upcoming. Runs on: script bundles.
  • What it finds: The React 18 internal __SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED.ReactCurrentOwner reference that a bundled jsx-runtime leaves in a build.
  • Why it matters: A bundled React 18 jsx-runtime builds element objects that React 19 rejects, which is the main reason the React 19 upgrade was reverted from 7.1.
  • Fix: Rebuild with a current @wordpress/scripts so react/jsx-runtime maps to the ReactJSXRuntime external (wp-react-jsx-runtime).

Class component uses string refs#

  • Severity: Medium. Confidence: Medium. Status: upcoming. Runs on: script bundles.
  • What it finds: Reads of this.refs.name.
  • Why it matters: React 19 removes string refs. Core plans a compatibility polyfill, so this may keep working for a while.
  • Fix: Replace ref="name" with createRef() or a callback ref.

Assigns defaultProps, which React 19 ignores on function components#

  • Severity: Info. Confidence: Low. Status: upcoming. Runs on: script bundles.
  • What it finds: Assignments to .defaultProps.
  • Why it matters: React 19 drops defaultProps for function components (class components keep it), and core plans a compatibility layer. The scanner cannot tell which kind of component this is, so treat it as a pointer only.
  • Fix: For function components, use default values in parameter destructuring: function Card( { size = "m" } ).
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