New FileFix Attack Exploits Windows File Explorer to Run Malicious Commands

Cybersecurity researcher Mr. D0x has developed FileFix, a novel social engineering attack that weaponizes Windows File Explorer’s address bar to execute malicious PowerShell commands.

This technique evolves the established ClickFix attack methodology by exploiting browser file-upload functionality to bypass traditional security warnings.

The attack chain begins when victims visit a phishing page disguised as a file-sharing notification (e.g., “HRPolicy.docx shared by mr.d0x”).

Technical Execution Mechanism

The attack leverages HTML’s <input type="file"> element to trigger File Explorer. When users click “Open File Explorer,” the page:

1. Copies a malicious PowerShell command to the clipboard using navigator.clipboard.writeText()
2. Opens File Explorer via the file-upload dialog
3. Instructs users to paste the “file path” into the address bar (auto-highlighted via Ctrl+L)

The PowerShell command uses comment concatenation to hide malicious activity:

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

Here, ping example.com represents the malicious payload (e.g., malware download), while text after # displays a decoy path.

File Explorer executes the command before the comment, rendering the malicious portion invisible to victims.

Attack Innovations and Evasion Techniques

FileFix introduces critical advancements in social engineering:

• MOTW (Mark of the Web) bypass: Executables run through File Explorer’s address bar shed MOTW warnings, enabling unsigned code execution
• File upload blocking: JavaScript intercepts file-selection attempts, forcing victims to use the address bar:

javascriptfileInput.addEventListener('change', () => {
  alert("Please follow the stated instructions.");
  fileInput.value = "";
  setTimeout(() => fileInput.click(), 500);
});

• Dual-path delivery: Variants combine command execution with automatic EXE downloads when the “Open File Explorer” button is clicked.

Enterprise Security Implications

This technique demonstrates heightened risk because:

1. It exploits trusted UI elements (File Explorer) rather than suspicious terminals
2. Commands originate from browser child processes (e.g., chrome.exe → cmd.exe), blending with legitimate activity
3. The attack requires no malware downloads initially, bypassing endpoint detection

Security teams should monitor for unusual cmd.exe/powershell.exe spawns from browser processes and educate users about the risks associated with address-bar execution.

Researchers confirm FileFix’s effectiveness against current Windows 11 builds, highlighting the persistent threat posed by social engineering innovations.

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