Comment 96 for bug 1850651

Tested in a fully up-to-date xenial amd64 VM. I verified that the version currently in xenial-updates (1:60.9.0+build1-0ubuntu0.16.04.2) exhibits the problem. I then enabled xenial-proposed, installed the thunderbird update (1:60.9.1+build1-0ubuntu0.16.04.1) and verified that the problem is fixed.

I'm sorry this fell off my radar and remained there lingering for so long.