express-mock-middleware through 0.0.6 is vulnerable to Prototype Pollution

express-mock-middleware through 0.0.6 is vulnerable to Prototype Pollution. Exported functions by the package can be tricked into adding or modifying properties of the `Object.prototype`. Exploitation of this vulnerability requires creation of a new directory where an attack code can be placed which will then be exported by `express-mock-middleware`. As such, this is considered to be a low risk.