---
id: CVE-2026-100639
title: >-
  SiYuan v3.8.3 fails to HTML-escape the data-subtype attribute when generating
  gutter-button markup (app/src/protyle/gutter/button.ts, assigned via innerHTML
  in app/src/protyle/gutter/index.ts) from content pasted as plain-text Markdown
  c…
summary: >-
  SiYuan v3.8.3 fails to HTML-escape the data-subtype attribute when generating
  gutter-button markup (app/src/protyle/gutter/button.ts, assigned via innerHTML
  in app/src/protyle/gutter/index.ts) from content pasted as plain-text Markdown
  c…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'
cwe:
  - CWE-79
vendor: siyuan-note
product: siyuan
affected:
  - siyuan < 3.8.4
published: '2026-09-26'
updated: '2026-09-26'
sourceUpdated: '2026-09-26T14:16:45.750'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-100639'
references:
  - url: >-
      https://github.com/siyuan-note/siyuan/security/advisories/GHSA-2cmm-9x9j-rvff
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/siyuan-before-3.8.4-cross-site-scripting-via-kramdown-ial
    label: disclosure@vulncheck.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-26T13:33:20.924Z'
---

## Overview

SiYuan v3.8.3 fails to HTML-escape the data-subtype attribute when generating gutter-button markup (app/src/protyle/gutter/button.ts, assigned via innerHTML in app/src/protyle/gutter/index.ts) from content pasted as plain-text Markdown containing a Kramdown inline attribute list (IAL). Because the shared Lute renderer parses Kramdown IAL from text/plain input, an attacker-supplied Markdown snippet using entity-encoded quotes in data-subtype breaks out of the attribute value when the gutter markup is re-parsed by the browser, injecting additional attributes such as autofocus and onfocus. If a victim pastes the crafted Markdown and the affected gutter control receives focus, the injected handler executes; in the Electron desktop application, where the main BrowserWindow enables Node integration and disables context isolation, this results in JavaScript execution with renderer Node.js privileges (remote code execution). Fixed in v3.8.4.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.