CVE-2026-33035

AVideo contains a reflected XSS vulnerability that allows unauthenticated attackers to execute arbitrary JavaScript in a victim's browser. User input from a URL parameter flows through PHP's json_encode() into a JavaScript function that renders it via innerHTML, bypassing encoding and achieving full script execution.

Root Cause

The vulnerability is caused by two issues working together:

1. Source: Unescaped user input passed to JavaScript (videoNotFound.php)

File: view/videoNotFound.php line 49

if (!empty($_REQUEST['404ErrorMsg'])) {
    echo 'avideoAlertInfo(' . json_encode($_REQUEST['404ErrorMsg']) . ');';
}

PHP's json_encode() with default flags only escapes quotes (" → \") and backslashes. It does NOT escape HTML special characters (<, >, /). The resulting string contains raw HTML tags that are passed directly to JavaScript.

2. Sink: innerHTML renders HTML tags as executable DOM (script.js)

File: view/js/script.js

function avideoAlertInfo(msg) {            // line ~1891
    avideoAlert("", msg, 'info');           // calls ↓
}

function avideoAlert(title, msg, type) {   // line ~1270
    avideoAlertHTMLText(title, msg, type);  // calls ↓
}

function avideoAlertHTMLText(title, msg, type) {  // line ~1451
    var span = document.createElement("span");
    span.innerHTML = msg;                  // line 1464, XSS SINK
    swal({ content: span });
}

innerHTML parses the string as HTML. Any <img>, <svg>, or other HTML tags with event handlers are instantiated as real DOM elements, triggering JavaScript execution.

Data Flow

URL parameter (?404ErrorMsg=PAYLOAD)
    → $_REQUEST['404ErrorMsg']
    → json_encode()          ← does NOT escape < > /
    → avideoAlertInfo()
    → avideoAlert()
    → avideoAlertHTMLText()
    → span.innerHTML = msg   ← renders HTML tags, executes JS

Proof of Concept

https://localhost/view/videoNotFound.php?404ErrorMsg=<img src=x onerror=alert(document.domain)>

The page renders:

avideoAlertInfo("<img src=x onerror=alert(document.domain)>");

Which flows to span.innerHTML = "<img src=x onerror=alert(document.domain)>". The browser creates an <img> element, src=x fails to load, onerror fires alert(document.domain).

Affected Code

The innerHTML sink exists in 4 functions. Any future code that passes user input to avideoAlertInfo(), avideoAlertWarning(), avideoAlertDanger(), or avideoAlertSuccess() will create additional XSS vectors.

Fix 1: Escape HTML in PHP (source fix)

// view/videoNotFound.php line 49
// BEFORE (vulnerable):
echo 'avideoAlertInfo(' . json_encode($_REQUEST['404ErrorMsg']) . ');';

// AFTER (fixed):
echo 'avideoAlertInfo(' . json_encode($_REQUEST['404ErrorMsg'], JSON_HEX_TAG | JSON_HEX_AMP) . ');';

JSON_HEX_TAG converts < → \u003C and > → \u003E, preventing HTML injection.

Fix 2: Use textContent instead of innerHTML (sink fix, recommended)

// view/js/script.js - all alert functions
// BEFORE (vulnerable):
span.innerHTML = msg;

// AFTER (fixed):
span.textContent = msg;

textContent treats the string as plain text, HTML tags are displayed literally, never parsed or executed.

Fix 3: Add Content-Security-Policy header (defense in depth)

Content-Security-Policy: default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'

• Session hijacking, steal PHPSESSID cookie (not HttpOnly by default)
• Account takeover, use stolen session to change password or email
• Phishing, inject a realistic login form inside the SweetAlert modal
• Worm propagation, inject self-spreading payloads via comments/messages
• Admin compromise, send crafted link to admin, steal session, gain full control

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

Kodem intelligence

1. What is CVE-2026-33035? CVE-2026-33035 is a medium-severity cross-site scripting (XSS) vulnerability in wwbn/avideo (composer), affecting versions <= 25.0. No fixed version is listed yet. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. Which versions of wwbn/avideo are affected by CVE-2026-33035? wwbn/avideo (composer) versions <= 25.0 is affected.
3. Is there a fix for CVE-2026-33035? No fixed version is listed for CVE-2026-33035 yet. Monitor the advisory for updates and apply mitigations in the interim.
4. Is CVE-2026-33035 exploitable, and should I be worried? Whether CVE-2026-33035 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-33035 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-33035? No fixed version is listed yet. In the interim: Validate and encode untrusted input before rendering it as HTML. Applying a Content Security Policy reduces the impact if encoding is bypassed.

Other vulnerabilities in wwbn/avideo