While loading a profile in Chrome Developer Tools on a file that violates a policy the URL is unknown in the incident and UI popup.
This happens due to how DLP hooks in to the open file dialog and registers that as an HTTPs upload. This only occurs when the Dev Tools are undocked in a separate window.
The workaround is to load the profile while dev tools is docked in the chrome browser window. Admins can then add a whilelist URL to the policy or configuration for whichever page is open to avoid an incident / block message.