Creating a new bug report and selecting a file owned by root and having perms of 600 as common user and clicking on "attach" does nothing - therefore did not inform the user about the culprit. The user should be faced with an error message.
This is probably one that you'll have to talk to bugzilla upstream about, it's probably not local setup-specific.
That is one you'll have to talk to your browser vendor about.
ok - if it is not a (local) config issue, yes, ofc
https://bugzilla.mozilla.org/show_bug.cgi?id=1052614