A newly identified exploit, known as “FileFix,” is causing considerable concern within the cybersecurity sector due to its clever manipulation of Windows File Explorer to execute harmful commands, all while remaining within the confines of a web browser.
Created by security researcher mr.d0x, FileFix represents a creative advancement of the infamous ClickFix social engineering attack, showcasing how even trusted system functionalities can be weaponized by malicious actors.
How FileFix Works
In contrast to traditional ClickFix attacks, which require users to paste commands into the Windows Run Dialog (Win+R), FileFix cleverly utilizes the file upload feature commonly found on various websites.
When a victim interacts with an “Open File Explorer” or “Choose File” button on a phishing site, the Windows File Explorer dialog is triggered.
The twist lies in the attacker’s instructions, which prompt the user to copy a seemingly innocuous file path and paste it into the File Explorer address bar.
Unbeknownst to the user, this path conceals a malicious PowerShell command, artfully hidden after a comment in the address bar. For instance, the phishing page might guide the user with the following steps:
- Copy the file path below:
C:companyinternal-securefiledriveHRPolicy.docx - Open File Explorer and select the address bar (CTRL + L)
- Paste the file path and press Enter
However, what is actually copied to the clipboard is:
Powershell.exe -c ping example.com # C:companyinternal-securefiledriveHRPolicy.docxWhen this command is pasted into the address bar and executed, Windows runs the PowerShell command, while the dummy file path following the hash (#) obscures 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:
C:companyinternal-securefiledriveHRPolicy.docx
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:companyinternal-securefiledriveHRPolicy.docx");
});
// Copy command and open File Explorer
fileExplorer.addEventListener('click', function() {
navigator.clipboard.writeText("Powershell.exe -c ping example.com # C:companyinternal-securefiledriveHRPolicy.docx");
fileInput.click();
});
// Block actual file uploads
fileInput.addEventListener('change', () => {
alert("Please follow the stated instructions.");
fileInput.value = "";
setTimeout(() => fileInput.click(), 500);
});
This script ensures that users cannot upload a file, instead repeatedly prompting them to adhere to the attacker’s instructions.
Why FileFix Is Dangerous
FileFix poses a unique threat as it exploits familiar workflows—file uploads and the Windows File Explorer—allowing it to bypass user skepticism.
This attack does not necessitate elevated privileges or complex malware; it relies solely on straightforward social engineering and the user’s trust in standard Windows dialogs.
Furthermore, Chrome’s process tree reveals that cmd.exe is spawned directly from the browser session, confirming the execution of the command.
Security experts caution that FileFix could facilitate the delivery of infostealers, ransomware, or other forms of malware, and its stealthy nature renders it a significant risk for both individuals and organizations.
How to Stay Safe
- Be cautious of instructions that ask you to copy and paste file paths or commands, particularly from unfamiliar sources.
- Monitor for suspicious child processes (e.g., cmd.exe, powershell.exe) initiated by browsers.
- Keep security software updated and educate users about emerging social engineering tactics.
As cybercriminals continue to innovate, maintaining vigilance and enhancing user awareness remain the most effective defenses against exploits like FileFix.
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