md-editor-v3: XSS via fenced-code language rendering bypass (CVE-2026-84992) | HOL Guard CVE

Medium · CVSS 6.1CVE-2026-84992GHSA-3RM2-H79C-8QW6

md-editor-v3: XSS via fenced-code language rendering bypass

Answer in brief

CVE-2026-84992 records a Medium severity (CVSS 6.1) vulnerability in md-editor-v3: XSS via fenced-code language rendering bypass. The current sources do not mark it as known exploited. The current feed maps imzbf/md-editor-v3 (generic), md-editor-v3 (npm), md-editor-v3 (npm). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 18, 2026Updated Sep 18, 2026Source checked Sep 18, 2026First seen by HOL Sep 18, 2026Material review Sep 18, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.1
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 6.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps imzbf/md-editor-v3 (generic), md-editor-v3 (npm), md-editor-v3 (npm). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
imzbf/md-editor-v3generic	< 6.5.4	Not reported
md-editor-v3npm	<=6.5.3	6.5.4
md-editor-v3npm	>=0 <6.5.4	6.5.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for imzbf/md-editor-v3, md-editor-v3, md-editor-v3.
Review the reported fix. Update md-editor-v3 to 6.5.4; md-editor-v3 to 6.5.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 18, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 18, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 18, 2026

Sources and claim methodology

Upstream source 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

Quoted source text, attributed separately from HOL analysis.