What’s Vulnerable › Vulnerabilities

CVE-2026-84992: md-editor-v3: XSS via fenced-code language rendering bypass

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-18 · updated 2026-09-24
• Weakness: CWE-79

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

Affected products

• imzbf md-editor-v3: before 6.5.4

References

• https://github.com/imzbf/md-editor-v3/commit/2c07360420e74087f5bc63032ab155d93e0a0b10
• https://github.com/imzbf/md-editor-v3/releases/tag/v6.5.4
• https://github.com/imzbf/md-editor-v3/security/advisories/GHSA-3rm2-h79c-8qw6
• https://github.com/imzbf/md-editor-v3/security/advisories/GHSA-3rm2-h79c-8qw6

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