So when using qs.parse and passing in an object to expand out the top-level keys, if somewhere in the value is a circular reference, it will fail with RangeError: Maximum call stack size exceeded. Here is a simple example:

var a = {}; a.b = a;
qs.parse({
  'foo[bar]' = 'baz',
  'foo[baz]' = a
})

I'm really only reporting this because it used to work with the old qs library. It was reported to me here: expressjs/connect-multiparty#11 (comment)