The class com.insecureshop.WebViewActivity contains the following code. As per the code, the application registers a path webview and a query parameter url. The application implements a URL validation and only allows URLs that ends with insecureshopapp.com to be loaded in Webview.
Since the application implements a weak host validation, a malicious application can bypass the host validation by loading arbitrary URL owned by attacker that ends with insecureshopapp.com. In such a case something like attackerinsecureshopapp.com would stand valid.