Plate: Media embed provider metadata can bypass URL sanitization and execute iframe JavaScriptGHSA-qj6x-xx2h-8hvv
HIGHFix: udecode/plate#5014GHSA-qj6x-xx2h-8hvv is a high-severity (CVSS 8.7) Cross-site Scripting (XSS) vulnerability in @platejs/media. A fix is available for @platejs/media — see the affected versions and patch details below.
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-qj6x-xx2h-8hvv.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-qj6x-xx2h-8hvv by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 384,993 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@platejs/medianpmDescription
Summary
The media embed renderer trusts serialized provider or sourceUrl metadata and skips the URL protocol validation that normally blocks unsafe media embed URLs. A crafted Plate document can set a known video provider while keeping url as a javascript: iframe source. When a victim opens that document in an app using the registry media embed component, the component renders the attacker URL directly as an iframe src.
Impact
An attacker who can create or share Plate document content with another user can execute JavaScript in the victim browser context when the victim opens the document. This can expose application data available to the page and perform actions as the victim, depending on the host application's session model.
Reproduction
Use a Plate editor or viewer that renders media embeds with the registry MediaEmbedElement and load a document containing this node:
{
"type": "media_embed",
"provider": "vimeo",
"sourceUrl": "https://vimeo.com/1",
"url": "javascript:parent.postMessage('plate-media-xss','*')",
"children": [{ "text": "" }]
}
When rendered, the node is treated as a Vimeo media embed because provider is present. The iframe receives the unvalidated url value as its src.
Root Cause / Technical Details
parseMediaUrl is the intended hardening point for media embed URLs and rejects parser output unless the URL protocol is http: or https:. However, useMediaState had a fast path for serialized nodes that already contain provider or sourceUrl. That fast path returned { id, provider, sourceUrl, url } directly and did not call parseMediaUrl or otherwise validate the stored url.
The registry MediaEmbedElement then checks that embed.provider is one of the video providers and renders non-YouTube video providers with <iframe src={embed.url}>. Because provider is attacker-controlled serialized document metadata, it can be set to vimeo while url remains javascript:....
This is fixed in @platejs/media 53.1.4 by recomputing embed metadata from the render URL instead of trusting serialized provider, id, or sourceUrl metadata.
PoC Evidence
A browser proof using the same data flow set an iframe src to:
javascript:parent.postMessage('plate-media-xss','*')
Chromium executed the iframe JavaScript and the parent page received plate-media-xss, confirming execution from the iframe source.
Remediation
Upgrade @platejs/media to 53.1.4 or later. Treat provider, sourceUrl, and id in serialized documents as untrusted derived metadata. Recompute embed metadata from url with parseMediaUrl, or at minimum validate any fast-path url with the same protocol allowlist before rendering an iframe.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @platejs/media | ≥ 53.0.0&&< 53.1.4 | 53.1.4npm install @platejs/media@53.1.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @platejs/media, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @platejs/media to 53.1.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-qj6x-xx2h-8hvv is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is GHSA-qj6x-xx2h-8hvv in your dependencies?
Find it across npm, including transitive dependencies.