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Monstra 3.0.4 has Stored XSS via Uploading html file that has no extension. #459

Hexife opened this Issue Oct 25, 2018 · 1 comment


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2 participants

Hexife commented Oct 25, 2018

Brief of this vulnerability
In uploading process, Monstra file filter allow to upload no-extension file. If html file that has no extension, it can be executed in browser as html, and it causes of Stored XSS.

Test Environment

  • Apache/2.4.18 (Debian)
  • PHP (cli)

Affect version


  1. move to http://[address]:[port]/[app_path]/admin/index.php?id=filesmanager with admin credential

  2. Save php codes with no extensions. and upload it like below.

# xss
<html><head><title>Monstra XSS</title></head><body><script>alert('xss');</script></body></html>
  1. Click the uploaded file name or
    move to http://[address]:[port]/[app_path]/public/uploads/[uploaded file].
  • Monstra CMS append '.' behind to upload file name when upload file has no extension
  1. Profit!

Reason of This Vulnerability
Monstra prevent to upload php-style files using extension filer in uploading process at ./plugins/box/filesmanager/filesmanager.admin.php like below.

    if ($_FILES['file']) {
        if ( ! in_array(File::ext($_FILES['file']['name']), $forbidden_types)) {
            $filepath = $files_path.Security::safeName(basename($_FILES['file']['name'], File::ext($_FILES['file']['name'])), null, false).'.'.File::ext($_FILES['file']['name']);
            $uploaded = move_uploaded_file($_FILES['file']['tmp_name'], $filepath);
            if ($uploaded !== false && is_file($filepath)) {
                Notification::set('success', __('File was uploaded', 'filesmanager'));
            } else {
                $error = 'File was not uploaded';
        } else {
            $error = 'Forbidden file type';
    } else {
        $error = 'File was not uploaded';

This filtering logic checks that extension of upload file is in their blacklist($forbidden_type variable), but it is not check that extension do not exist in their logic.

Following this logic, No extension file saved with appending '.' at end of filename (e.g. xss -> xss.)

It can be executed in browser(I tested in Chrome ver 68.0.3440.106 (Official Build, 64-bit)) as html and JavaScript.

It can be executed in browser as html, and it causes of Stored XSS.


This comment has been minimized.

DanielRuf commented Nov 15, 2018

Ouch. Very unfortunate to see that all these security issues are not resolved and no reaction from the devs.

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