The unnamed "popular and widely-deployed application" appears to be Firefox and Thunderbird: <a href="https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=949644" rel="nofollow">https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=949644</a><p>There's more discussion here: <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1607902" rel="nofollow">https://bugzilla.mozilla.org/show_bug.cgi?id=1607902</a>