An XSS in statics-server <= 0.0.9 can be used via injected iframe in the filename when statics-server displays directory index in the browser. Statics-server does not implement any HTML escaping when displays directory index in the browser. Variable v is used in <a href> element without escaping, which allows to embed HTML <iframe> tag with src attribute points to another HTML file in the directory. This file can contain malicious JavaScript code, which will be executed:

// ./node_modules/statics-server/index.js, line 18:

    if(fs.lstatSync(staticPath).isDirectory()){
        var files=fs.readdirSync(staticPath);
        var lis='';
        files.forEach((v,i)=>{
            if(fs.lstatSync(path.resolve(staticPath,v)).isDirectory()){
                lis+=`<li><a href="${req.url}${v}/">${v}/</a></li>`;
            }else {
                lis+=`<li><a href="${req.url}${v}">${v}</a></li>`
            }
        });

        (...)

References

• https://nvd.nist.gov/vuln/detail/CVE-2018-3771
• https://hackerone.com/reports/355458