CVE-2026-84992 md-editor-v3: XSS via fenced-code language rendering bypass
An attacker can execute JavaScript in the application origin by supplying crafted Markdown with malicious fenced-code language attributes to the md-editor-v3 library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-84992?
CVE-2026-84992 is a medium-severity cross-site scripting vulnerability in imzbf md-editor-v3, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
md-editor-v3 is a Markdown editor for Vue 3 developed in JSX and TypeScript. Prior to 6.5.4, MdPreview's useMarkdownIt() highlight callback in packages/MdEditor/layouts/Content/composition/useMarkdownIt.ts inserts a fenced-code language value into class and language HTML attributes without escaping or consistently quoting it. Both highlighted and non-highlighted rendering paths reach this return value, while XSSPlugin filters only existing html_block and html_inline tokens before rendering and therefore cannot inspect the renderer-generated HTML. An attacker who can supply Markdown can use crafted fenced-code metadata to execute JavaScript in the application origin when a victim renders it, including as stored cross-site scripting when the host persists the Markdown. This issue is fixed in version 6.5.4
Weakness: CWE-79
Which versions are affected by CVE-2026-84992?
2 open source packages ship an affected version, including md-editor-v3.
| Package | Affected | Fixed in |
|---|---|---|
md-editor-v3 npm | All versions | 6.5.4 |
md-editor-v3 npm | All versions | 6.5.4 |
How do I fix CVE-2026-84992?
Upgrade md-editor-v3 to 6.5.4 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-84992 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-84992 exists.
Sources
Also known as GHSA-3rm2-h79c-8qw6.