When using certain blank characters in a URL, they where incorrectly rendered as spaces instead of an encoded URL. This vulnerability affects Firefox < 77.
https://www.mozilla.org/security/advisories/mfsa2020-20/
https://bugzilla.mozilla.org/show_bug.cgi?id=1629506