Version 18.104.22.168 is being released to all customers today. It fixes one issue that is triggered when accessing an ftp:// url from the browser in explicit proxy mode. Although it's only one issue, it has affected a number of customers and can cause browsing interruptions, so we thought we should release it as soon as possible.
The release notes for this version can be found here: http://swa.sophos.com/rn/swa/concepts/ReleaseNotes_22.214.171.124.html
You can find release notes for all past updates here: http://swa.sophos.com/rn/