CVE-2026-33035

WWBN AVideo is an open source video platform. In versions 25.0 and below, there is 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. The vulnerability is caused by two issues working together: unescaped user input passed to JavaScript (videoNotFound.php), and innerHTML rendering HTML tags as executable DOM (script.js). The attack can be escalated to steal session cookies, take over accounts, phish credentials via injected login forms, spread self-propagating payloads, and compromise admin accounts — all by exploiting the lack of proper input sanitization and cookie security (e.g., missing HttpOnly flag on PHPSESSID). The issue has been fixed in version 26.0.

WWBN AVideo is an open source video platform. In versions 25.0 and below, there is 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. The vulnerability is caused by two issues working together: unescaped user input passed to JavaScript (videoNotFound.php), and innerHTML rendering HTML tags as executable DOM (script.js). The attack can be escalated to steal session cookies, take over accounts, phish credentials via injected login forms, spread self-propagating payloads, and compromise admin accounts — all by exploiting the lack of proper input sanitization and cookie security (e.g., missing HttpOnly flag on PHPSESSID). The issue has been fixed in version 26.0.

Summary

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)>

<img width="1918" height="1035" alt="image" src="https://github.com/user-attachments/assets/20077ce2-5b49-4bd3-a7df-ab48be786cc1" />

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

| File | Line | Issue | |------|------|-------| | view/videoNotFound.php | 49 | json_encode() does not escape < > for HTML context | | view/js/script.js | 1464 | span.innerHTML = msg renders user input as HTML | | view/js/script.js | 1282 | span.innerHTML = msg in avideoAlertWithCookie() | | view/js/script.js | 1335 | span.innerHTML = __(msg,true) in avideoConfirm() | | view/js/script.js | 1358 | span.innerHTML = msg in avideoAlertOnceForceConfirm() |

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.

Remediation

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…

WWBN AVideo is an open source video platform. In versions 25.0 and below, there is 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. The vulnerability is caused by two issues working together: unescaped user input passed to JavaScript (videoNotFound.php), and innerHTML rendering HTML tags as executable DOM (script.js). The attack can be escalated to steal session cookies, take over accounts, phish credentials via injected login forms, spread self-propagating payloads, and compromise admin accounts — all by exploiting the lack of proper input sanitization and cookie security (e.g., missing HttpOnly flag on PHPSESSID). The issue has been fixed in version 26.0.

WWBN AVideo is an open source video platform. In versions 25.0 and below, there is 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. The vulnerability is caused by two issues working together: unescaped user input passed to JavaScript (videoNotFound.php), and innerHTML rendering HTML tags as executable DOM (script.js). The attack can be escalated to steal session cookies, take over accounts, phish credentials via injected login forms, spread self-propagating payloads, and compromise admin accounts — all by exploiting the lack of proper input sanitization and cookie security (e.g., missing HttpOnly flag on PHPSESSID). The issue has been fixed in version 26.0.

Summary

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)>

<img width="1918" height="1035" alt="image" src="https://github.com/user-attachments/assets/20077ce2-5b49-4bd3-a7df-ab48be786cc1" />

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

| File | Line | Issue | |------|------|-------| | view/videoNotFound.php | 49 | json_encode() does not escape < > for HTML context | | view/js/script.js | 1464 | span.innerHTML = msg renders user input as HTML | | view/js/script.js | 1282 | span.innerHTML = msg in avideoAlertWithCookie() | | view/js/script.js | 1335 | span.innerHTML = __(msg,true) in avideoConfirm() | | view/js/script.js | 1358 | span.innerHTML = msg in avideoAlertOnceForceConfirm() |

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.

Remediation

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…