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StarCitizenWiki Extension Embed Video: Stored XSS via unsanitized service name in exception text

High severity GitHub Reviewed Published Jun 19, 2026 in StarCitizenWiki/mediawiki-extensions-EmbedVideo • Updated Jun 19, 2026

Package

composer starcitizenwiki/embedvideo (Composer)

Affected versions

<= 4.0.0

Patched versions

4.1.0

Description

Summary

When passing an unknown service name to embedvideo, an error message is rendered containing the invalid service name. The service name is not sanitized and can contain HTML.

Details

There is a hardcoded list of allowed services in a switch statement inside EmbedServiceFactory#newFromName here. When the service name is not known, an exception is thrown with the service name injected into the message via sprintf here. This message is not sanitized and is marked as isHtml here. Similarly with {{evl: here.

PoC

// Must be on a page, not on ExpandTemplates
{{#ev:<img src=x onerror=alert(document.domain)>|dQw4w9WgXcQ}}
{{#evl:id=dummy|service=<img src=x onerror=alert(document.domain)>}}

Impact

Stored XSS that allows arbitrary Javascript/HTML insertion on any page that a user can edit. It requires no interaction and executes in the wiki origin for every visitor to the page.

References

@octfx octfx published to StarCitizenWiki/mediawiki-extensions-EmbedVideo Jun 19, 2026
Published to the GitHub Advisory Database Jun 19, 2026
Reviewed Jun 19, 2026
Last updated Jun 19, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS score

Weaknesses

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Learn more on MITRE.

Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as <, >, and & that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages. Learn more on MITRE.

CVE ID

CVE-2026-55690

GHSA ID

GHSA-c29q-5xm7-5p62

Source code

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