Ignores invalid query param part

lib/plausible_web/controllers/api/external_controller.ex

@@ -83,7 +83,7 @@ defmodule PlausibleWeb.Api.ExternalController do
     else
       uri = params["url"] && URI.parse(params["url"])
       host = if uri && uri.host == "", do: "(none)", else: uri && uri.host
-      query = if uri && uri.query, do: URI.decode_query(uri.query), else: %{}
+      query = decode_query_params(uri)
 
       ref = parse_referrer(uri, params["referrer"])
       country_code = visitor_country(conn)
@@ -347,4 +347,15 @@ defmodule PlausibleWeb.Api.ExternalController do
        do: true
 
   defp right_uri?(_), do: false
+
+  defp decode_query_params(nil), do: nil
+  defp decode_query_params(%URI{query: nil}), do: nil
+
+  defp decode_query_params(%URI{query: query_part}) do
+    try do
+      URI.decode_query(query_part)
+    rescue
+      _ -> nil
+    end
+  end
 end

test/plausible_web/controllers/api/external_controller_test.exs

@@ -688,6 +688,22 @@ defmodule PlausibleWeb.Api.ExternalControllerTest do
       assert pageview.utm_source == "%balle%"
     end
 
+    test "ignores invalid query param part", %{conn: conn} do
+      params = %{
+        n: "pageview",
+        u:
+          "https://test.com/?utm_source=Bing%20%7C%20Text%20%7C%20Leads%20%7C%20EIGEN%20NAAM-most%20broad%20(Various%20search%20term%20matches)%20%7C%20Afweging,%20Consumptie%20%7C%20T%3A%",
+        d: "invalid-query-test.com"
+      }
+
+      conn = post(conn, "/api/event", params)
+
+      assert conn.status == 202
+
+      pageview = get_event("invalid-query-test.com")
+      assert pageview.utm_source == ""
+    end
+
     test "can use double quotes in query params", %{conn: conn} do
       q = URI.encode_query(%{"utm_source" => "Something \"quoted\""})