49/100 CVSS 8.6 🔴 CVE ANALYSISPublished: June 19, 2026

StarCitizenWiki Extension Embed Video: Stored XSS via unsanitized class passed to template

### 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/inc...

8.6

CVSS Score

MEDIUM

Threat Level

Priority /100

TBD

Exploited ITW

Monitor

CISA Status

Sources

🔵

HIGH-PRIORITY SECURITY ADVISORY — Priority Score: 49/100

CVSS 8.6 MEDIUM. SENTINEL APEX recommends immediate patch evaluation. Intelligence from 1 confirmed source(s).

📋 Executive Summary

⚡ Analyst Assessment — SENTINEL APEX v4.0

CYBERDUDEBIVASH SENTINEL APEX has confirmed a MEDIUM-tier threat intelligence signal for CVE-2026-55691 affecting composer starcitizenwiki/embedvideo. Composite threat score: 49/100. Intelligence corroborated across 1 source(s): github_advisories. CVSS base score: 8.6. Exploitation probability assessed as HIGH based on vulnerability characteristics.

Intelligence sources: github_advisories

⚠️ Business Impact Analysis

⚠️ composer starcitizenwiki/embedvideo users face material security risk requiring immediate remediation

🔗 Attack Chain Analysis

Step-by-step attack chain based on observed TTPs and vulnerability characteristics:

#	Phase	Attacker Action	MITRE
1	Reconnaissance	Attacker identifies exposed starcitizenwiki/embedvideo instances via Shodan, Censys, or targeted scanning	`TA0043`
2	Initial Access	Exploitation of CVE-2026-55691 in composer starcitizenwiki/embedvideo	`T1190`
3	Persistence	Backdoor, scheduled task, or new admin account created for persistent access	`T1053`
4	Command & Control	Attacker establishes persistent C2 channel using HTTPS or DNS tunneling	`T1071`
5	Impact / Objectives	Intellectual property theft, espionage, cryptomining, or preparation for future attack stage	`T1657`

⚠ Deep Dive Analysis

This high-severity vulnerability in composer starcitizenwiki/embedvideo (CVSS 8.6) represents a significant attack surface. SENTINEL APEX assesses exploitation to be technically feasible with moderate effort. Organizations running starcitizenwiki/embedvideo in internet-facing or privileged positions face immediate risk.

SENTINEL APEX URGENCY: HIGH. Score: 49/100 MEDIUM. Patch before exploitation activity begins.

🎯 MITRE ATT&CK Mapping

Category	Mapping
Primary Tactic	Initial Access
Primary Technique	T1190 — Exploit Public-Facing Application
Sub-Technique	T1203 — Exploitation for Client Execution
Weakness (CWE)	CWE-79
Intel Type	🔴 CVE ANALYSIS
Source(s)	github_advisories

🔴 CVE Reference

CVE ID	Reference	Score
CVE-2026-55691	NVD →	8.6
CVE-2026-55691	NVD →	8.6

🏷️ Indicators of Compromise — Enriched IOC Feed

Normalized IOCs with confidence scoring. Block immediately across all enforcement points. SOC Pro subscribers receive enriched IOC bundles with full attribution and STIX/TAXII feeds.

Indicator Value	Type	Confidence	First Seen
a573a16d925ee0ea0d34b360856dc8ab0b88f822	sha1	90%	2026-06-19
https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/blob/a573a16d	url	82%	2026-06-19

🔍 Detection Rules — Sigma (SIEM)

Deploy to Splunk, Elastic, Microsoft Sentinel, or QRadar. SOC Pro subscribers receive pre-compiled SIEM-native query packs updated with each pipeline run.

Sigma YAMLtitle: CVE-2026-55691 Exploitation Attempt — composer starcitizenwiki/embedvideo
id: 6b3d3d47ce3cff32-e1cb
status: experimental
description: Detects exploitation of CVE-2026-55691 in composer starcitizenwiki/embedvideo. Priority: MEDIUM. Score: 49/100
author: CYBERDUDEBIVASH SENTINEL APEX v4.0 (bivash@cyberdudebivash.com)
date: 2026-06-19
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-55691
    - https://blog.cyberdudebivash.in/
tags:
    - attack.initial_access
    - attack.t1190
    - cve-2026-55691
    - cve-2026-55691
logsource:
    category: webserver
detection:
    keywords:
        - 'CVE-2026-55691'
        - 'CVE-2026-55691'
        - 'cve-2026-55691'
    condition: keywords
falsepositives:
    - Security scanners
level: high

📡 Detection Rules — YARA (Endpoint)

Deploy to endpoint detection platforms. Enterprise subscribers receive tuned, FP-validated YARA rule packs.

YARArule CVE_2026_55691_Exploitation {
    meta:
        description = "Detects artifacts related to CVE-2026-55691 exploitation in composer starcitizenwiki/embedvideo"
        author      = "CYBERDUDEBIVASH SENTINEL APEX v4.0"
        date        = "2026-06-19"
        severity    = "HIGH"
        cvss        = "8.6"
        priority    = "49/100"
        threat_level = "MEDIUM"
        reference   = "https://nvd.nist.gov/vuln/detail/CVE-2026-55691"
    strings:
        $id_str  = "CVE-2026-55691" ascii nocase
        $product = "starcitizenwiki_embedvideo" ascii nocase wide
    condition:
        any of them
}

🛡️ SOC Response Playbook

1IMMEDIATE (0-1hr): Identify all instances of starcitizenwiki/embedvideo in your environment via CMDB/asset inventory
2IMMEDIATE: Block all 2 IOCs in this report at firewall, proxy, DNS, and EDR simultaneously
3IMMEDIATE (0-1hr): Apply vendor patch — no maintenance window exception for MEDIUM threats
4IMMEDIATE (1-2hr): If no patch available: implement WAF rules, ACLs, or network-level compensating controls
5SHORT-TERM (2-4hr): Deploy Sigma detection rule to SIEM — validate alert generation in test environment
6SHORT-TERM (4-8hr): Review logs for exploitation indicators (anomalous starcitizenwiki/embedvideo requests, error spikes)
7SHORT-TERM (8-24hr): Hunt for post-exploitation: new admin accounts, scheduled tasks, lateral movement
8MONITOR: Subscribe to composer security advisories for patch updates
9ONGOING: Track SENTINEL APEX intelligence feed for follow-on campaigns targeting starcitizenwiki/embedvideo

📎 Intelligence References

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⚡ CYBERDUDEBIVASH SENTINEL APEX v4.0

Intelligence report generated by CYBERDUDEBIVASH SENTINEL APEX v4.0
Report ID: SENTINEL-CVE-2026-55691-2026-06-19 | Priority: 49/100 MEDIUM | Sources: 1
© 2026 CYBERDUDEBIVASH PRIVATE LIMITED
Republication requires written attribution to CYBERDUDEBIVASH SENTINEL APEX

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