Updated to version 1.6.6
Changelog:

    added new AutoScroll plugin
    added new F12 shortcut for Web Inspector
    fixed: correctly switching between tabbars when closing tabs
    fixed: draw tabbar base even when there are no tabs in main tabbar
    fixed: position of add tab button when there are no tabs in main
tabbar
    mac: define application category in Info.plist
    windows: load font.ttf (if exists) and use it as app font
    linux: fixed setting correct paths for portable mode

    fixed build issues on Mac
    fixed error handling when downloading CA certificates bundle
    fixed error handling when downloading AdBlock subscriptions
    fixed loading KWalletPasswords plugin

    enabled sending DoNotTrack header by default
    updated ca-bundle certificates
    use same session files with both Qt4 and Qt5
    fixed: Click2Flash playing videos on YouTube with Qt5
    fixed: hiding close button on current tab when dragging it with Qt5
    fixed: double clicking on scroll buttons in tabbar with Qt5
    fixed: text visibility in speeddial inputs with dark themes
    fixed: getting tab index with rtl layout
    fixed: ctrl+up shortcut in websearchbar correctly select first item
    fixed: correctly loading translations of all plugins