I dont know if it's helping but here is what is happening when i click on a link in Thunderbird 52.6.0 using SolydX EE OS
Output of: sudo journalctl -kaf --no-hostname | grep -w 'apparmor="DENIED"' fév 11 17:31:49 kernel: audit: type=1400 audit(1518388309.673:180): apparmor="DENIED" operation="exec" profile="thunderbird" name="/opt/firefox/firefox" pid=26794 comm="thunderbird" requested_mask="x" denied_mask="x" fsuid=1000 ouid=0 Jean
