REST Service call getLoggedInUser only shows account from key
I am working on a project using PCS. I have created a webform and the goal now is to load the logged in user into the web form, so that it cannot be adapted when a user logs in. The problem is when I use /bpm/api/4.0/identities/loggedInUser (https://docs.oracle.com/en/cloud/paas/process-cloud/cprrb/op-identities-loggedinuser-get.html), it only shows the user that I have entered in the security field of the REST service created in PCS-Integrations.
How can I get the log in of the user that truly is logged in, instead of the credentials that I have filled in the security?