The second point release update to our LTS release 16.04 is out now. This contains all the bugfixes added to 16.04 since its first release in April. Users of 16.04 can run the normal update procedure to get these bugfixes. In addition, we suggest adding the Backports PPA to update to Plasma 5.8.5. Read more about it: http://kubuntu.org/news/plasma-5-8-5-bugfix-release-in-xenial-and-yakkety-backports-now/
Warning: 14.04 LTS to 16.04 LTS upgrades are problematic, and should not be attempted by the average user. Please install a fresh copy of 16.04.2 instead. To prevent messages about upgrading, change Prompt=lts with Prompt=normal or Prompt=never in the /etc/update-manager/release-upgrades file. As always, make a thorough backup of your data before upgrading.