Where is ENDPOINT_AUTH_PARAMETER_SYSTEMVSSCONNECTION_ACCESSTOKEN configured?

I am using "Publish test results" task in my build definitions since long time, but I have recently noticed that this task is giving a warning when trying to publish the test results.

##[warning]Failed to publish test run data:  An error occurred while sending the request.
The remote server returned an error: (403) Forbidden.

When investigating in the task source code (this last calls vsts-task-lib/tasks), I have noticed that there is a call to https://mysubscription.visualstudio.com/ using a token named ENDPOINT_AUTH_PARAMETER_SYSTEMVSSCONNECTION_ACCESSTOKEN and I suppose this user does not have enough permissions, but I do not know where and with which user this token has been configured.

Could you please tell if you have any idea, where this ENDPOINT_AUTH_PARAMETER_SYSTEMVSSCONNECTION_ACCESSTOKEN token is configured ?