Log Message:
Update to 68.3.1

Changelog:
68.3.1
Changes
changed
In dark theme unread messages no longer shown in blue to distinguish from tagged \ 
messages

changed
Account setup is now using client side DNS MX lookup instead of relying on a server.

Fixes
fixed
Searching LDAP address book crashed in some circumstances

fixed
Message navigation with backward and forward buttons did not work in some \ 
circumstances

fixed
WebExtension toolbar icons were displayed too small

fixed
Calendar: Tasks due today were not listed in bold

fixed
Calendar: Last day of long-running events was not shown

68.3.0
What’s New
new
Message display toolbar action WebExtension API

new
Navigation buttons are now available in content tabs, for example those opened \ 
via an add-on search

Changes
changed
"New email" icon in Windows systray changed from in-tray with arrow to \ 
envelope
Fixes

fixed
Icons of attachments in the attachment pane of the Write window not always correct

fixed
Toolbar buttons of add-ons in the menubar not shown after startup

fixed
LDAP lookup not working when SSL was enabled. LDAP search not working when \ 
"All Address Books" was selected.

fixed
Scam link confirmation panel not working

fixed
In Write window, the Link Properties dialog wasn't showing named anchors in \ 
context menu

fixed
Calendar: Start-up failed if the application menu is not on the calendar toolbars

fixed
Chat: Account reordering via drag-and-drop not working on Instant messaging \ 
status dialog (Show Accounts)

fixed
Various security fixes

Security fixes:
#CVE-2019-17008: Use-after-free in worker destruction
#CVE-2019-13722: Stack corruption due to incorrect number of arguments in WebRTC code
#CVE-2019-11745: Out of bounds write in NSS when encrypting with a block cipher
#CVE-2019-17009: Updater temporary files accessible to unprivileged processes
#CVE-2019-17010: Use-after-free when performing device orientation checks
#CVE-2019-17005: Buffer overflow in plain text serializer
#CVE-2019-17011: Use-after-free when retrieving a document in antitracking
#CVE-2019-17012: Memory safety bugs fixed in Firefox 71, Firefox ESR 68.3, and \ 
Thunderbird 68.3