###You should leave it as is.
You should leave it as is.
target="_blank"
is a security vulnerability. In previous versions, you had to fix this yourself but in Sitecore 8.2 onwards, this is the default behaviour.
More information here: Adding rel=”noopener” to Sitecore
Edited to add: Your clarified behaviour, however, is clearly a bug and should be taken to Sitecore Support.