Links to ".." can be broken in iframes

We have a mini site resource that has a link to a new page inside a folder. In this new page there is a link to ".." to go back to index. This link doesn't work.

I checked it and it seems the problem is that the navigation to the new page doesn't change the iframe URL, and IIRC we use that URL to calculate the path for relative URLs.

How to reproduce:

1. Go to 34 > MM Dev > Resource: File > Another mini-site with files in folders and relative links back 
2. Click "Etiquette".
3. Scroll to the bottom and click "Index page".