Stored XSS in AVideo CustomizeUser Plugin Field Names

AVideo through commit c3edcc274c389816d434acadac07ee78eaf330c1 contains a stored cross-site scripting vulnerability in the CustomizeUser plugin where the field_name parameter is stored raw without sanitization. Administrators can inject malicious scripts via the add.json.php endpoint that execute when viewing extra info pages or profile forms that render the typeToHTML function.

Casky was already ahead

This CVE exploits attack patterns that Casky's 323matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

CVE-2026-89254 is a stored cross-site scripting (XSS) vulnerability in AVideo's CustomizeUser plugin that allows administrators to inject malicious JavaScript through unsanitized field_name parameters via the add.json.php endpoint. The vulnerability persists in the application database and executes whenever users view extra info pages or profile forms that utilize the typeToHTML rendering function. This affects all AVideo installations with the CustomizeUser plugin enabled, particularly impacting self-hosted video platforms where administrator accounts may be compromised or malicious insiders exist. The high CVSS score of 8.7 reflects the severity—stored XSS can lead to session hijacking, credential theft, malware distribution, and lateral movement within the organization.

Casky's 323 matched security skills leverage Claude AI's extended reasoning to detect the attack patterns underlying this vulnerability across MITRE ATT&CK's Initial Access (TA0001) and Privilege Escalation (TA0043) techniques. Practitioners using Casky would identify CWE-79 violations through static analysis of parameter handling in add.json.php, dynamic detection of unsanitized database writes, and behavioral patterns indicating script injection attempts. The platform flags suspicious POST requests to the CustomizeUser endpoint, monitors typeToHTML function calls for injected payloads, and detects anomalous script execution in user context during profile rendering. Security teams gain visibility into the full attack chain—from malicious payload injection to persistent code execution—enabling rapid remediation before widespread compromise.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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Composite risk scoring from EPSS, CISA KEV, Shodan, and GreyNoise — 21 security APIs correlated into a single Casky Risk Score. Coming in Casky Pro. Join early access →

323 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-89254.

Abuse of Public-Facing API: Mobile API Abuse

mobile security · low

Run

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

MITRE ATT&CK Techniques

TA0001 TA0043

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