FileFix - A ClickFix Alternative Summary:
Summary:
Security researcher mrd0x highlighted a novel social engineering method, dubbed ‘FileFix,’ that capitalizes on the common File Upload functionality seen on websites, with the unique twist of using the File Explorer window to execute malicious commands. Unlike ClickFix, a widely used tactic by threat actors that employs bogus error messages or CAPTCHA verification to entice victims into copying and pasting a malicious script into the Windows Run dialog, FileFix exploits the File Explorer address bar, which can be used to execute OS commands. The attack chain initiates when a user clicks the "Choose File" button on a website, triggering File Explorer to open. The attacker can then pre-load a malicious command into the clipboard and instruct the user to paste it into the File Explorer address bar. To guide the user through the process, attackers can provide simple, convincing instructions such as: "Copy this file path, open File Explorer, select the address bar (CTRL + L), and paste the path to access the file." In this case, the attacker’s PowerShell command is cleverly disguised by appending it after the file path, making it appear to the user as though they're simply accessing a file.
According to mrd0x, attackers can also weaponize FileFix to deliver and launch malicious payloads directly. For instance, the phishing page can silently download an executable file to the user’s default Downloads directory, then copy the file path to the clipboard and trigger the File Explorer window. The user, following the attacker’s instructions, would paste the path into the address bar and unknowingly execute the malicious file.
Security Officer Comments:
A notable aspect of FileFix is its ability to bypass certain security measures, such as the Mark of The Web attribute, which is typically applied to files downloaded from external sources. When executables are launched through the File Explorer address bar, this attribute is stripped away, making it harder for security software to detect the file as a potential threat. While browsers and security tools like Microsoft Defender SmartScreen or Google Safe Browsing may issue warnings before saving the file, attackers may still succeed by exploiting user inattention or persistence through multiple prompts.
mrd0x noted that the user may also intentionally or accidentally select a file for upload, given that is the intended purpose of the File Upload functionality. In this case, an actor can create a script to intercept that action, clear the file input field, and immediately reopen the File Explorer window, keeping the user engaged in the attack flow.
Although the FileFix technique is sophisticated and offers a new avenue for social engineering, we have yet to see it being employed in attacks in the wild. However, attackers may begin leveraging this technique, especially as it exploits common user behaviors with minimal interaction needed.
Suggested Corrections:
To defend against potential FileFix attacks, organizations should implement a combination of user awareness training and technical controls. Educating users to avoid pasting unknown paths or commands into the File Explorer address bar is crucial, especially if prompted by unfamiliar websites. On the technical side, endpoint protection tools should monitor unusual command execution patterns, such as cmd[.]exe or powershell[.]exe being spawned from browser processes. Furthermore, disabling clipboard access for untrusted web content and restricting execution of files lacking trusted digital signatures can further reduce the attack vector.
Link(s):
https://mrd0x.com/filefix-clickfix-alternative/
Security researcher mrd0x highlighted a novel social engineering method, dubbed ‘FileFix,’ that capitalizes on the common File Upload functionality seen on websites, with the unique twist of using the File Explorer window to execute malicious commands. Unlike ClickFix, a widely used tactic by threat actors that employs bogus error messages or CAPTCHA verification to entice victims into copying and pasting a malicious script into the Windows Run dialog, FileFix exploits the File Explorer address bar, which can be used to execute OS commands. The attack chain initiates when a user clicks the "Choose File" button on a website, triggering File Explorer to open. The attacker can then pre-load a malicious command into the clipboard and instruct the user to paste it into the File Explorer address bar. To guide the user through the process, attackers can provide simple, convincing instructions such as: "Copy this file path, open File Explorer, select the address bar (CTRL + L), and paste the path to access the file." In this case, the attacker’s PowerShell command is cleverly disguised by appending it after the file path, making it appear to the user as though they're simply accessing a file.
According to mrd0x, attackers can also weaponize FileFix to deliver and launch malicious payloads directly. For instance, the phishing page can silently download an executable file to the user’s default Downloads directory, then copy the file path to the clipboard and trigger the File Explorer window. The user, following the attacker’s instructions, would paste the path into the address bar and unknowingly execute the malicious file.
Security Officer Comments:
A notable aspect of FileFix is its ability to bypass certain security measures, such as the Mark of The Web attribute, which is typically applied to files downloaded from external sources. When executables are launched through the File Explorer address bar, this attribute is stripped away, making it harder for security software to detect the file as a potential threat. While browsers and security tools like Microsoft Defender SmartScreen or Google Safe Browsing may issue warnings before saving the file, attackers may still succeed by exploiting user inattention or persistence through multiple prompts.
mrd0x noted that the user may also intentionally or accidentally select a file for upload, given that is the intended purpose of the File Upload functionality. In this case, an actor can create a script to intercept that action, clear the file input field, and immediately reopen the File Explorer window, keeping the user engaged in the attack flow.
Although the FileFix technique is sophisticated and offers a new avenue for social engineering, we have yet to see it being employed in attacks in the wild. However, attackers may begin leveraging this technique, especially as it exploits common user behaviors with minimal interaction needed.
Suggested Corrections:
To defend against potential FileFix attacks, organizations should implement a combination of user awareness training and technical controls. Educating users to avoid pasting unknown paths or commands into the File Explorer address bar is crucial, especially if prompted by unfamiliar websites. On the technical side, endpoint protection tools should monitor unusual command execution patterns, such as cmd[.]exe or powershell[.]exe being spawned from browser processes. Furthermore, disabling clipboard access for untrusted web content and restricting execution of files lacking trusted digital signatures can further reduce the attack vector.
Link(s):
https://mrd0x.com/filefix-clickfix-alternative/