NoScript blocks PDFs in frames unless their ancestors are Javascript-allowed

Steps to reproduce the issue:

1. Open Stock Tor Browser 7.5a4.
2. Set the security setting to Low.
3. Visit https://web.archive.org/save/https://svn.torproject.org/svn/projects/design-paper/tor-design.pdf, after some time PDF should show up.
4. Set the security setting to Medium.
5. Refresh the page.
6. PDF wont show up no matter how much you wait :(

There's nothing in the stuff that is disabled at Medium security setting that would cause the PDF to not show up, so this is most definitely a bug.