CVE-2026-63671

@nuxtjs/mdc: the URL sanitizer misses SVG xlink:href and data:text/html, allowing XSS from untrusted markdown at the default configuration

Published Sep 16, 2026 CVSS 3.1 · 8.1 High EPSS < 1% KEV · Not listed
Description
MDC is a tool to take regular Markdown and write documents interacting deeply with a Vue component. Prior to 0.22.1, @nuxtjs/mdc uses parseMarkdown with allowDangerousHtml enabled by default and relies on validateProps, validateProp, and unsafeLinkPrefix to remove executable URLs from untrusted Markdown. validateProp checks only attributes named href or src, allowing an SVG xlink:href value represented as xLinkHref to retain a javascript: URL that executes in the page origin when selected. The data:text/html denylist entries are also compared against url.protocol, which is only data:, so an iframe src containing data:text/html survives sanitization and executes in an opaque origin when loaded. Plain href javascript: URLs, srcdoc, object, script, and base elements are already blocked, making these two paths specific sibling gaps in the sanitizer. This issue is fixed in version 0.22.1.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-mxm6-v9r6-r94c @nuxtjs/mdc's URL sanitizer misses SVG xlink:href and data:text/html, allowing XSS from untrusted markdown at the default configuration
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Nuxt-content
Nuxt-content mdc
Vendors & Products Nuxt-content
Nuxt-content mdc
Type Values Removed Values Added
Description MDC is a tool to take regular Markdown and write documents interacting deeply with a Vue component. Prior to 0.22.1, @nuxtjs/mdc uses parseMarkdown with allowDangerousHtml enabled by default and relies on validateProps, validateProp, and unsafeLinkPrefix to remove executable URLs from untrusted Markdown. validateProp checks only attributes named href or src, allowing an SVG xlink:href value represented as xLinkHref to retain a javascript: URL that executes in the page origin when selected. The data:text/html denylist entries are also compared against url.protocol, which is only data:, so an iframe src containing data:text/html survives sanitization and executes in an opaque origin when loaded. Plain href javascript: URLs, srcdoc, object, script, and base elements are already blocked, making these two paths specific sibling gaps in the sanitizer. This issue is fixed in version 0.22.1.
Title @nuxtjs/mdc: the URL sanitizer misses SVG xlink:href and data:text/html, allowing XSS from untrusted markdown at the default configuration
Weaknesses CWE-184
CWE-79
References
Metrics cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Sep 18, 2026, 5:54 PM
Reserved
Jul 17, 2026, 2:47 PM
Status
Deferred
Published
Sep 16, 2026, 3:17 PM
Modified
Sep 24, 2026, 9:25 PM