We just recently published a security update to the LTS version 1.0. It contains some important fixes and improvements we backported from the master version. See the details in the release notes .
This release is considered stable and we recommend to update all productive installations of Roundcube 1.0.x with this version if you're unable to upgrade to a more recent series. Download it from GitHub via https://roundcube.net/download.
As usual, don’t forget to backup your data before updating!