The X-XSS-Protection HTTP header is a basic protection against XSS. It was originally by Microsoft but Chrome has since adopted it as well.
This middleware sets the X-XSS-Protection header. On modern browsers, it will set the value to 1; mode=block. On old versions of Internet Explorer, this creates a vulnerability (see here and here), and so the header is set to 0 to disable it.
To use this middleware:
var xssFilter = require('x-xss-protection')
app.use(xssFilter())To force the header to be set to 1; mode=block on all versions of IE, add the option:
app.use(xssFilter({ setOnOldIE: true }))
// This has some security problems for old IE!