In June 2025, cybersecurity researcher mr.d0x unveiled a novel social engineering technique named FileFix, which manipulates Windows File Explorer’s address bar to execute malicious commands. This method represents an evolution of the earlier ClickFix attacks, introducing a more deceptive approach that exploits user trust in familiar system interfaces.
Understanding the FileFix Attack
The FileFix attack begins with a phishing webpage designed to appear as a legitimate file-sharing notification. For instance, a user might encounter a message stating, HRPolicy.docx shared by mr.d0x. This message prompts the user to open File Explorer to access the shared document.
Upon clicking the provided link, the webpage performs two key actions:
1. Clipboard Manipulation: The site uses JavaScript to copy a malicious PowerShell command to the user’s clipboard without their knowledge.
2. File Explorer Invocation: Simultaneously, the site opens the File Explorer window through the browser’s file upload functionality.
The user is then instructed to paste the file path into the File Explorer’s address bar. Unbeknownst to them, this file path is actually the malicious command copied earlier. When pasted and executed, the command runs, potentially compromising the system.
Technical Execution Mechanism
The attack leverages the HTML `` element to trigger File Explorer. When users click Open File Explorer, the page:
1. Copies a Malicious PowerShell Command: Utilizing `navigator.clipboard.writeText()`, the site copies a command to the clipboard.
2. Opens File Explorer: Through the file-upload dialog, File Explorer is launched.
3. Instructs User Action: The user is guided to paste the file path into the address bar, which is auto-highlighted via Ctrl+L.
The PowerShell command is crafted to include a comment that disguises the malicious activity:
“`
powershell.exe -c ping example.com # C:\company\internal-secure\filedrive\HRPolicy.docx
“`
In this example, `ping example.com` is the malicious payload, while the text after `#` serves as a decoy path. File Explorer executes the command before the comment, rendering the malicious portion invisible to the user.
Innovations and Evasion Techniques
FileFix introduces several advancements in social engineering:
– Bypassing Mark of the Web (MOTW): Files executed through File Explorer’s address bar do not carry MOTW attributes, allowing unsigned code to run without security warnings.
– Blocking File Uploads: JavaScript intercepts file-selection attempts, forcing users to use the address bar:
“`javascript
fileInput.addEventListener(‘change’, () => {
alert(Please follow the stated instructions.);
fileInput.value = ;
setTimeout(() => fileInput.click(), 500);
});
“`
– Dual-Path Delivery: Variants combine command execution with automatic executable downloads when the Open File Explorer button is clicked.
Enterprise Security Implications
This technique poses significant risks because:
1. Exploitation of Trusted Interfaces: It manipulates familiar UI elements like File Explorer, making the attack less suspicious.
2. Stealthy Command Execution: Commands originate from browser child processes (e.g., `chrome.exe → cmd.exe`), blending with legitimate activities.
3. Bypassing Initial Malware Downloads: The attack doesn’t require initial malware downloads, evading endpoint detection systems.
Security teams should monitor for unusual `cmd.exe` or `powershell.exe` executions originating from browser processes and educate users about the risks associated with address-bar execution.
Mitigation Measures
To defend against FileFix and similar attacks:
– User Education: Train staff to avoid pasting commands into unfamiliar interfaces, including File Explorer.
– Enhanced Monitoring: Configure security tools to detect command executions from non-standard entry points.
– Restrict Clipboard Access: Implement policies to block clipboard-based and browser-initiated scripts that can pass commands to system components.
By understanding and mitigating the FileFix attack vector, organizations can bolster their defenses against evolving social engineering threats.
