CVE-2026-55691

highpriority · track · 0EPSS 0.005 · 42 %ileUS
grimoire priorityP2 · Scheduled
Exploitable?
—
no known exploitation
Likely / severe?
0.48% (42nd) EPSS
CVSS 8.6 · high
Is it mine?
1 products
Check your exposure
Who says so?
1 sources
osv

EPSS · scored 2026-10-28

The EmbedVideo Extension is a MediaWiki extension which adds a parser function called #ev and various parser tags for embedding video clips from various video sharing services. Prior to 4.1.0, EmbedHtmlFormatter::toHtml in includes/EmbedService/EmbedHtmlFormatter.php passes the user-supplied class value directly to sprintf while constructing a figure element. A quote in the class value can terminate the class attribute and inject arbitrary HTML attributes or markup into the rendered page. A user able to edit a wiki page can store JavaScript that executes for visitors who render the affected content. This issue is fixed in version 4.1.0.

01

cvss

Technical severity, 0–10. One row per scoring source.

8.6
010

base score 0–10 · higher = more severe · hover a vector to decode

v3.18.6highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:Lsecondary · security-advisories@github.comexploitability 3.9 · impact 4.7
v3.18.6highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:Lsecondary · OSV
v3.17.9highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L/E:Usecondary · CVSS-BT (t0sche)
02

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: poc · Automatable: yes · Technical Impact: partialcoordinatorcisa_ssvcUS
03

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-79USCWE-79USCWE-80US
04

affected products (1)

Products and version ranges known to be affected.

05

advisories (1)

Vendor and ecosystem advisories describing this.

  • GHSA-7h5p-637f-jfr7StarCitizenWiki Extension Embed Video: Stored XSS via unsanitized class passed to template2026-06-19ghsa · osvUS

    ### Summary The user supplied class value is fed directly into the sprintf call that creates HTML. You can add a quote to escape the class and then inject arbitrary html/javascript to the final output. ### Details The template [here](https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/blob/a573a16d925ee0ea0d34b360856dc8ab0b88f822/includes/EmbedService/EmbedHtmlFormatter.php#L138) adds a figure with a class that is substituted in. This value is provided to sprintf [here](https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/blob/a573a16d925ee0ea0d34b360856dc8ab0b88f822/includes/EmbedService/EmbedHtmlFormatter.php#L156), an unescaped version of the class supplied by the user. ``` $template = <<<HTML <figure class="%s" data-service="%s" %s %s> <div class="embedvideo-wrapper" %s>%s%s%s</div>%s </figure> HTML; ``` ### PoC Note the double quote immediately following the single quote to escape the class attribute in the template: ``` <youtube class='" onmouseover="alert(document.domain)' id="dQw4w9WgXcQ">dQw4w9WgXcQ</youtube> ``` ### Impact Arbitrary HTML can be inserted into the DOM by any user on any page, allowing for JavaScript to be executed.

06

sources

Which sources assert this record, and when.

osvNVDCVE.orgMITRE
published 2026-09-15modified 2026-09-30
07

references (3) nvd

External citations — patches, advisories, analysis.

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