CVE-2026-58263

Jodit Editor is a WYSIWYG editor with a built-in file browser & image editor. In versions prior to 4.12.28, the built-in clean-html sanitizer can be bypassed by a MathML/<style> carrier that hides a dangerous element from the sanitizer's element walk, so a no-interaction event handler survives into the editor value, potentially causing Mutation XSS. When an application supplies attacker-influenced HTML to the editor's value-set or insertion paths, the sanitized output still contains a live <img ... onload=...> (or another non-onerror handler such as onfocus). A consumer that renders that output (element.innerHTML = editor.value) executes the handler with no user interaction. This issue has been fixed in version 4.12.28.

Jodit Editor is a WYSIWYG editor with a built-in file browser & image editor. In versions prior to 4.12.28, the built-in clean-html sanitizer can be bypassed by a MathML/<style> carrier that hides a dangerous element from the sanitizer's element walk, so a no-interaction event handler survives into the editor value, potentially causing Mutation XSS. When an application supplies attacker-influenced HTML to the editor's value-set or insertion paths, the sanitized output still contains a live <img ... onload=...> (or another non-onerror handler such as onfocus). A consumer that renders that output (element.innerHTML = editor.value) executes the handler with no user interaction. This issue has been fixed in version 4.12.28.

Summary

jodit's built-in clean-html sanitizer can be bypassed by a MathML/<style> carrier that hides a dangerous element from the sanitizer's element walk, so a no-interaction event handler survives into the editor value. When an application supplies attacker-influenced HTML to the editor's value-set or insertion paths, the sanitized output still contains a live <img ... onload=...> (or another non-onerror handler such as onfocus). A consumer that renders that output (element.innerHTML = editor.value) executes the handler with no user interaction. This is a stored cross-site scripting vulnerability, confirmed live on the shipped es2021/jodit.min.js for 4.12.25 and the latest 4.12.27 (in Chromium via a client-side innerHTML consumer, and in Firefox via server-rendered / document-context output; see the cross-browser note under Proof of concept).

Details

The bypass exploits the order in which clean-html parses, walks, and re-serializes the value.

1. On the value-set path, the clean-html plugin handles :beforeSetNativeEditorValue (src/plugins/clean-html/clean-html.ts:116), parsing the value into an inert document: sandBox.innerHTML = data.value.

2. In that parse, the source nesting math > mtext > table > mglyph > style triggers MathML text-integration-point and foster-parenting rules: the <img> is parsed as text inside <style> (rawtext), not as an element. The <table> is foster-parented out, and the <mglyph> MathML text-integration point governs the namespace, so the <img> never becomes an element node in this parse.

3. That value-set sanitizer is safeHTML (src/core/helpers/html/safe-html.ts:24); it walks the tree but acts on elements only (the Dom.isElement gate at :39) and runs against the parse-1 sandBox, in which the <img> is rawtext, not an element. So removeAllEventAttributes (the full on* strip at safe-html.ts:76) has no element to clean and the handler passes through. The onBeforeSetNativeEditorValue handler runs safeHTML on that parse-1 tree both before and after it captures the value, so neither pass ever sees the <img> as an element.

4. The captured value (data.value = sandBox.innerHTML) is then assigned to the editable, a second parse, which hoists the <img> out of <style> and into the HTML namespace as a live element with its handler intact. The serialize-reparse moves the element across the tree and across namespaces:

BEFORE - parse 1 (sandBox): the <img> is <style> text
  <math>          [MathML]
    <mtext>       [MathML]
      <mglyph>    [HTML]      integration point: content parses as HTML
        <style>   [HTML]      text "<img ... onload=...>"   <-- <img> is RAWTEXT, not an element
      <table>     [HTML]

AFTER - editor.value (re-parsed): the <img> is hoisted OUT of <style>, live
  <p>             [HTML]
    <math>        [MathML]
      <mtext>     [MathML]
        <mglyph>  [MathML]
          <style> [MathML]    (now empty)
        <img>     [HTML]      <-- hoisted out, HTML namespace, LIVE -> its handler fires
        <table>   [HTML]

5. editor.value now carries that live element. The value-set pass (Steps 1-4) only walked the parse-1 sandBox and never sees it; the other sanitizer, the on-change visitor (visitNodeWalker via a LazyWalker, clean-html.ts:56/:70), does reach the hoisted element, but its sanitizeAttributes filter calls sanitizeHTMLElement (safe-html.ts:139), which strips onerror only - it never reads the removeEventAttributes flag sanitizeAttributes passes it (sanitize-attributes.ts:30), so it never runs the full on* strip. So onload, onfocus, and every other non-onerror handler is never removed and persists in editor.value permanently. (onerror is the one handler the cleaner removes, but only after a ~300ms window in which it too fires.)

The two code points (jodit 4.12.27):

// 1. clean-html.ts onBeforeSetNativeEditorValue - the SYNCHRONOUS value-set pass…

Jodit Editor is a WYSIWYG editor with a built-in file browser & image editor. In versions prior to 4.12.28, the built-in clean-html sanitizer can be bypassed by a MathML/<style> carrier that hides a dangerous element from the sanitizer's element walk, so a no-interaction event handler survives into the editor value, potentially causing Mutation XSS. When an application supplies attacker-influenced HTML to the editor's value-set or insertion paths, the sanitized output still contains a live <img ... onload=...> (or another non-onerror handler such as onfocus). A consumer that renders that output (element.innerHTML = editor.value) executes the handler with no user interaction. This issue has been fixed in version 4.12.28.

Jodit Editor is a WYSIWYG editor with a built-in file browser & image editor. In versions prior to 4.12.28, the built-in clean-html sanitizer can be bypassed by a MathML/<style> carrier that hides a dangerous element from the sanitizer's element walk, so a no-interaction event handler survives into the editor value, potentially causing Mutation XSS. When an application supplies attacker-influenced HTML to the editor's value-set or insertion paths, the sanitized output still contains a live <img ... onload=...> (or another non-onerror handler such as onfocus). A consumer that renders that output (element.innerHTML = editor.value) executes the handler with no user interaction. This issue has been fixed in version 4.12.28.

Summary

jodit's built-in clean-html sanitizer can be bypassed by a MathML/<style> carrier that hides a dangerous element from the sanitizer's element walk, so a no-interaction event handler survives into the editor value. When an application supplies attacker-influenced HTML to the editor's value-set or insertion paths, the sanitized output still contains a live <img ... onload=...> (or another non-onerror handler such as onfocus). A consumer that renders that output (element.innerHTML = editor.value) executes the handler with no user interaction. This is a stored cross-site scripting vulnerability, confirmed live on the shipped es2021/jodit.min.js for 4.12.25 and the latest 4.12.27 (in Chromium via a client-side innerHTML consumer, and in Firefox via server-rendered / document-context output; see the cross-browser note under Proof of concept).

Details

The bypass exploits the order in which clean-html parses, walks, and re-serializes the value.

1. On the value-set path, the clean-html plugin handles :beforeSetNativeEditorValue (src/plugins/clean-html/clean-html.ts:116), parsing the value into an inert document: sandBox.innerHTML = data.value.

2. In that parse, the source nesting math > mtext > table > mglyph > style triggers MathML text-integration-point and foster-parenting rules: the <img> is parsed as text inside <style> (rawtext), not as an element. The <table> is foster-parented out, and the <mglyph> MathML text-integration point governs the namespace, so the <img> never becomes an element node in this parse.

3. That value-set sanitizer is safeHTML (src/core/helpers/html/safe-html.ts:24); it walks the tree but acts on elements only (the Dom.isElement gate at :39) and runs against the parse-1 sandBox, in which the <img> is rawtext, not an element. So removeAllEventAttributes (the full on* strip at safe-html.ts:76) has no element to clean and the handler passes through. The onBeforeSetNativeEditorValue handler runs safeHTML on that parse-1 tree both before and after it captures the value, so neither pass ever sees the <img> as an element.

4. The captured value (data.value = sandBox.innerHTML) is then assigned to the editable, a second parse, which hoists the <img> out of <style> and into the HTML namespace as a live element with its handler intact. The serialize-reparse moves the element across the tree and across namespaces:

BEFORE - parse 1 (sandBox): the <img> is <style> text
  <math>          [MathML]
    <mtext>       [MathML]
      <mglyph>    [HTML]      integration point: content parses as HTML
        <style>   [HTML]      text "<img ... onload=...>"   <-- <img> is RAWTEXT, not an element
      <table>     [HTML]

AFTER - editor.value (re-parsed): the <img> is hoisted OUT of <style>, live
  <p>             [HTML]
    <math>        [MathML]
      <mtext>     [MathML]
        <mglyph>  [MathML]
          <style> [MathML]    (now empty)
        <img>     [HTML]      <-- hoisted out, HTML namespace, LIVE -> its handler fires
        <table>   [HTML]

5. editor.value now carries that live element. The value-set pass (Steps 1-4) only walked the parse-1 sandBox and never sees it; the other sanitizer, the on-change visitor (visitNodeWalker via a LazyWalker, clean-html.ts:56/:70), does reach the hoisted element, but its sanitizeAttributes filter calls sanitizeHTMLElement (safe-html.ts:139), which strips onerror only - it never reads the removeEventAttributes flag sanitizeAttributes passes it (sanitize-attributes.ts:30), so it never runs the full on* strip. So onload, onfocus, and every other non-onerror handler is never removed and persists in editor.value permanently. (onerror is the one handler the cleaner removes, but only after a ~300ms window in which it too fires.)

The two code points (jodit 4.12.27):

// 1. clean-html.ts onBeforeSetNativeEditorValue - the SYNCHRONOUS value-set pass…