Demo:- https://file-smuggling.netlify.app/

This is a self-contained HTML app, handy, supports Windows, Mac, Linux and mobile.

It adopts HTML smuggling technique, leverages HTML5 and JavaScript to embed encoded file into HTML file, when user runs the JavaScript code in browser, it decodes the embedded payload, which, in turn, assembles the target file on the destination device.

You can convert your file to HTML encoded format, with password protected, then use it as email attachment or file download from web.

Download filesmugglingbuilder.html from this repository or try it online

(password is password)

https://github.com/gauravzack12/File-Smuggling (password is password)

When working with Javascript, the file can be created by using a Javascript Blob. A Blob is a representation of payload.

  var bobject = new Blob([payload], {type: 'octet/stream'});

It invoking the click action from within the Javascript, we mimic the user clicking on the link and starting the file download

  var hiddenobject = document.createElement('a');
  var url = window.URL.createObjectURL(bobject);
  hiddenobject.href = url;
  hiddenobject.download = targetfilename;
  hiddenobject.click();

Due to encoded patterns, no original file content passes through the network, bypassing email scanners, proxies and sandboxes.

As security admin, if you don't want user to bypass, you may fine tune the dection rule based on it's characteristics or simply block HTML file.

Reference

https://attack.mitre.org/techniques/T1027/006/

#html smuggling #payload #javascript #pentest #poc #html #smuggling #tool