In ESG, not logged in, navigate to a non-brokered dataset restful url for a privileged (admin permission required) task. (as if bookmarked or copied) E.g. Edit - upload files:
https://esg.prototype.ucar.edu/dataset/ucar.cgd.ccsm4.CESM_CAM5_BGC_LE.atm.proc.monthly_ave/bulkFileUploadForm.html

You will be prompted to log in. Log in as a user who lacks permission (e.g. cgrant).

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