Authorization Bypass Through User-Controlled Key vulnerability in elixir-grpc grpc allows authenticated attackers to access or modify resources belonging to other users by smuggling a conflicting value for any path-bound field via the query string or request body. In 'Elixir.GRPC.Server.Transcode':map_request/5 (lib/grpc/server/transcode.ex), all three clauses use Map.merge/2 with path bindings as the first argument, giving them the lowest merge precedence. A request such as GET /users/me/profile?user_id=victim (or a POST with {"user_id": "victim"} when body: "*") yields a decoded protobuf struct where the path-bound field carries the attacker-supplied value rather than the router-extracted value. Any handler that uses the path-bound field for authorization, multi-tenancy scoping, or ownership checks is silently bypassed. This issue affects grpc from 0.8.0 before 1.0.0.

stoatchat (delta/Revolt) versions from 20241213-1 before 20250210-1 allow users with only ViewChannel (read) permission on a channel to fetch that channel's webhooks, including their tokens, because the webhook fetch endpoint checked for ViewChannel instead of ManageWebhooks. Using a retrieved token, an attacker can send arbitrary messages to the channel, bypassing channel permissions and impersonating a bot or webhook. Fixed in 20250210-1 (0.8.2).