Fixes • Microsoft Office 365 accounts were unable to authenticate • Switching identities caused remote images in HTML signatures to not be shown • Thunderbird failed to import vCards that contained "\r\r\n" line endings • Contribution button for add-ons opened Contribution page in a Thunderbird tab, instead of the external browser • XMPP did not respond to unrecognized IQ queries, causing some servers to close the connection • Window titlebar buttons (minimize/maximize/close) were not displayed in Windows 10 "Dark" color mode • Various security fixes