CVE-2026-57440 is a high-severity (CVSS 7.5) Cross-site Scripting (XSS) vulnerability in starcitizenwiki/embedvideo. A fix is available for starcitizenwiki/embedvideo — see the affected versions and patch details below.
Mediawiki EmbedVideo Extension has stored XSS via malformed src url with $wgEmbedVideoRequireConsent disabled
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.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-57440.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-57440 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
starcitizenwiki/embedvideoReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Summary
With $wgEmbedVideoRequireConsent disabled (not the default), the urls for videos are passed into an iframe src attribute without sanitization. When given a malformed url or id, the src attribute can be escaped via double quotes, allowing for html/javascript injection.
Details
The iframe assembled here adds the url from getUrl() as the src without sanitization.
The id regex for the archiveorg service and the url regexes for the wistia and sharepoint services allow for double quotes to be introduced.
PoC
Using double quotes, the src attribute can be escaped.
<embedvideo service="archiveorg" id='a" onmouseover="alert(document.domain)" data-x="'></embedvideo>
Impact
When $wgEmbedVideoRequireConsent = false, any user able to edit a page can inject arbitrary JavaScript into an HTML event handler attribute (e.g. onfocus) via parameter. It requires no interaction (autofires via autofocus) and executes in the wiki origin for every visitor to the page.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | starcitizenwiki/embedvideo | all versions | 4.1.0composer require starcitizenwiki/embedvideo:^4.1.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for starcitizenwiki/embedvideo, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update starcitizenwiki/embedvideo to 4.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-57440 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 CVE-2026-57440 in your dependencies?
Find it across Packagist, including transitive dependencies.