In https://github.com/polcak/jsrestrictor/issues/133, there appeared the issue of cascading level-settings to nested iframes. 3bff977 partially solved the issue as it provided the way to cascade level settings from the parent window/frame to its nested iframes.

  +------------------------------------------------------------+
  | visited domain a.example                                   |
  |                                                            |
  | +--------------------------------------------------------+ |
  | | iframe from domain b.example                           | |
  | |                                                        | |
  | | +----------------------------------------------------+ | |
  | | | iframe from domain c.example                       | | |
  | | |                                                    | | |
  | | +----------------------------------------------------+ | |
  | |                                                        | |
  | +--------------------------------------------------------+ |
  +------------------------------------------------------------+

If the nested iframe belong to a domain with its custom settings, then this setting is applied to its iframe. But iframes nested in the iframe with different iframe inherit settings from the main window.

So even if domain B in the example has a specific settings, iframe C shares the settings with A.