lirantal/xss-in-serve-lite.md Secret

## xss-in-serve-lite.md

      
        

                
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              xss-in-serve-lite.md
            
          
        
      
      
    Cross-site scripting (XSS) vulnerability in serve-lite@1.1.0
serve-lite descibres itself as: a lightweight http-server for static file-based web development.
Observation:

Virtually zero downloads, so no considerable impact.
It was last published 6 months ago

Resources:

Project's GitHub source code: https://github.com/beenotung/serve-lite
Project's npm package: https://www.npmjs.com/package/serve-lite

Background on exploitation
This file server library is vulnerable to cross-site scripting because
when it detects a request to a directory it renders a file listing
of all of its contents with links that include the actual file names
without any sanitization or output encoding:
Lines 127-132 of server.js:
            for (let file of files) {
              let href = `${req.url}/${file}`.replace(/^\/\//, '/')
              let stat = fs.statSync(path.join(dir, file))
              let type = stat.isDirectory() ? 'D' : 'F'
              res.write(`[${type}] <a href="${href}">${file}</a><br>`)
            }
This vulnerability should probably be classified as a
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Proof of Concept exploit

Install the latest version of serve-lite (npm install --save lite-dev-server@1.1.0)
Make sure you have a public/ directory with files in it
Add a file into that directory named with an XSS payload in its name, such as touch '><img src=x onerror=alert(1)>'
Run the server node server.js 3000 public/
Browse to the webpage at http://localhost:3000/ and confirm an alert popup

Author
Liran Tal