Bigbug
Ah great!
The token is for CSRF protection, essentially stops a random website fooling you into deleting clients by browsing to itflow.example.com/post.php?delete_client=1. I wouldn't really consider it a bug, you had to actively seek out the token, and it changes on each login.
We can probably adjust the delete logic to only delete the client where the status is already archived though. Do you think it's necessary?