Yeah sorry, text or input fields... also iframe plugin... really anything that resembles "form data" or anything like that will always be drawn on top.
You have to be clever with making things turn invisible or move off-screen when not being used - or make something using spritefont and custom text field entry. This is not a limitation of Construct 2, it's just how HTML5 works in general. Unfortunately, there's not any "super easy" answer to solve the problem. In the past when I had this issue, I came up with clever ways to simply hide the input fields when they don't need to be used, then display them only when the user has to interact with them.