When more than two iframes loaded from forms with the same action are nested, after the second one, no additional iframe loads.

This issue occurs starting from the beta version of Firefox 132.0 (r20241018091619).

In the previous nightly version 132.0 (r20240908211800), this issue did not occur.

I believe Firefox is not considering the data sent via POST form to determine whether it should nest the iframe or not (it only does so based on the action URL).

As workaround, if you add a random query parameter to the action URL (e.g. ?[random]), it successfully loads indefinitely.

Add ?IFRAME_NAME_PLACEHOLDER at the end of the action URL in the test.html file to test this.

To reproduce this issue, use the following commands:

npm install

node server.js

Open firefox 132.0 and navigate to http://localhost:3000/test

• Push the button Submit and check the iframe content

Chrome	Firefox 132.0 nightly	Firefox 132.0 beta (or later)
129.0	132.0 nightly Sept 08	132.0 beta Oct 18
You can nest infinite iframes.	You can nest infinite iframes.	You can only nest two iframes. if you try to nest more, the second iframe won't load (the form doesn't submit)