Do not cross reference confidential issues
Summary
If i reference one issue in a confidential one there his a link to that confidential issue in the other one. I think as the issue is confidential that link should no be displayed at all.
At work i use a project in my personal GitLab space to handle some stuff related to my personal management. If i encounter a problem with a client on another project I will link to the issue with relative discussion for history purpose and discuss this with my managers later. The problem with this approach is that basically every time their is a problem on a project, the client can see that i referenced the issue somewhere else. This is a specific use case of course but it seems that a confidential issue and its references/links should not be displayed to anyone not having the right to see it for security reason.
I also note that the issue being confidential in my use case was not created as a confidential one; I later updated it. After that I tried to reference a new one in it and the reference appeared even tho it was a confidential one at the time.