It seems that a user without access to a certain project, can still see the information on issue linking on the Activity and All Tab.

To replicate this problem:

1. Create two projects, Project A and Project B
   • Project A has Browse Permission to Group (Anyone)
   • Project B has Browse Permission to Project Role (Developer)
   • And Project B has linking Permission: Project Role (Developer)
2. Create a ticket for both projects
3. A user belongs to the Project Role Developer link an issue from Project A to B
   • User who does not have access to project B should not know about the existence of Project B
4. The result/action of this issue linking will still be stored on the Activity and All tab

Tested this behavior on JIRA 4.4.1 and 5.0.5