After activating the default AppArmor profile for Firefox, links in e-mails on Thunderbird no longer work.
Expected behavior: When I click on a link in Thunderbird, Firefox starts (if necessary) and goes directly to the URL specified by the link.
Actual behavior: When I click on a link in Thunderbird, Firefox starts with an empty address bar, does not load any URL, and Firefox hangs. At that point, I have to kill Firefox from the command line. At this point, dmesg shows the following errors:
How do I instruct AppArmor to allow Firefox to load links clicked in Thunderbird?
Details: Ubuntu 20.04.1, Firefox 87.0, Thunderbird 78.7.1, default AppArmor profile from /etc/apparmor.d/usr.bin.firefox