Move a thread that Alice participated in to a forum that Alice has no access to. (Or revoke Alice's access to a forum she previously posted in.)
In this thread, move one of the posts by Alice to a new thread (within the same forum that Alice has no access to). Don't manually uncheck "Notify author of this action".
This results in a notification for Alice with a broken link to the inaccessible thread. But more importantly the notification leaks the title of...
