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Fencer Intel
high 8.6

CVE-2026-55691 json

EmbedVideo Extension : Stored XSS via unsanitized class passed to template

published 4mo ago modified last mo. also EUVD-2026-78832 , GHSA-7h5p-637f-jfr7

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits
0
none known

Summary

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.

Patch / fix

  • packagist starcitizenwiki/embedvideo 4.1.0
  • star-citizen embedvideo 4.1.0

Is CVE-2026-55691 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
last mo.

Exploit prediction

0.48% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/security/advisories/GHSA-7h5p-637f-jfr7 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L
GitHub 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L

Affected packages

ecosystem package affected fixed in
packagist starcitizenwiki/embedvideo
<4.1.0
4.1.0

Affected products

  • StarCitizenWiki mediawiki-extensions-EmbedVideo

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation
  • CWE-80 Improper Neutralization of Script-Related HTML Tags in a Web Page

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.