Grafana's data source proxy did not apply role-based access control to write requests forwarded to Loki data sources. A user holding only the Viewer role on an affected Grafana instance could send POST, PUT and DELETE requests through the proxy to the Loki rules API (/loki/api/v1/rules), allowing them to create, modify and delete Loki alerting rules. Because those rules are stored by Loki rather than by Grafana, the change took effect for every user of that Loki data source, not only for the Viewer who made the request. Exploitation requires an authenticated Viewer account on the Grafana inst