The Live Bookmarks page and the PDF viewer can run injected script content if a user pastes script from the clipboard into them while viewing RSS feeds or PDF files. This could allow a malicious site to socially engineer a user to copy and paste malicious script content that could then run with the context of either page but does not allow for privilege escalation. This vulnerability affects Firefox < 60.
https://www.mozilla.org/security/advisories/mfsa2018-11/
https://usn.ubuntu.com/3645-1/
https://bugzilla.mozilla.org/show_bug.cgi?id=1436482