The extension provides a public proxy endpoint that fetches a URL on behalf of the visitor. For one HTTP request method, the endpoint does not apply the authorization check that protects the other methods, so the URL it fetches is fully controlled by the requester. An unauthenticated attacker can make the server send requests to arbitrary internal or external hosts. The attacker receives the status code and selected response headers, which allows probing of internal hosts and ports. Response bodies are not disclosed.