diff --git a/lib/plausible_web/controllers/api/stats_controller.ex b/lib/plausible_web/controllers/api/stats_controller.ex
index 9d471c664b82..ab3f74209745 100644
--- a/lib/plausible_web/controllers/api/stats_controller.ex
+++ b/lib/plausible_web/controllers/api/stats_controller.ex
@@ -1647,7 +1647,9 @@ defmodule PlausibleWeb.Api.StatsController do
          _opts
        )
        when is_integer(segment_id) do
-    case ensure_expected_segment_filter_present(conn.params, segment_id) do
+    case conn.params
+         |> get_filters_param()
+         |> ensure_expected_segment_filter_present(segment_id) do
       :ok ->
         conn
 
@@ -1661,11 +1663,24 @@ defmodule PlausibleWeb.Api.StatsController do
 
   defp validate_required_filters_plug(conn, _opts), do: conn
 
+  defp get_filters_param(%{"filters" => filters} = _params) when is_binary(filters) do
+    JSON.decode!(filters)
+  end
+
+  defp get_filters_param(%{"filters" => filters} = _params) when is_list(filters) do
+    filters
+  end
+
+  defp get_filters_param(_params) do
+    nil
+  end
+
   defp ensure_expected_segment_filter_present(
-         %{"filters" => filters} = _params,
+         filters,
          expected_segment_id
-       ) do
-    case JSON.decode!(filters) do
+       )
+       when is_list(filters) do
+    case filters do
       [["is", "segment", [segment_id]] | _other_filters] when segment_id == expected_segment_id ->
         :ok
 
@@ -1674,7 +1689,7 @@ defmodule PlausibleWeb.Api.StatsController do
     end
   end
 
-  defp ensure_expected_segment_filter_present(_params, _expected_segment_id) do
+  defp ensure_expected_segment_filter_present(_filters, _expected_segment_id) do
     :error
   end
 
diff --git a/test/plausible_web/controllers/api/stats_controller/query_controller_test.exs b/test/plausible_web/controllers/api/stats_controller/query_controller_test.exs
new file mode 100644
index 000000000000..d7bab5c17d9b
--- /dev/null
+++ b/test/plausible_web/controllers/api/stats_controller/query_controller_test.exs
@@ -0,0 +1,137 @@
+defmodule PlausibleWeb.Api.InternalController.QueryTest do
+  use PlausibleWeb.ConnCase, async: false
+  use Plausible.Repo
+
+  describe "POST /api/:domain/query shared/public" do
+    test "returns aggregated metrics for public site", %{conn: conn} do
+      site = new_site(public: true)
+
+      populate_stats(site, [
+        build(:pageview, user_id: 5, pathname: "/foo", timestamp: ~N[2021-01-01 00:00:00])
+      ])
+
+      conn =
+        post(conn, "/api/stats/#{URI.encode(site.domain)}/query", %{
+          "metrics" => ["pageviews"],
+          "date_range" => "all",
+          "filters" => [["is", "event:page", ["/foo"]]]
+        })
+
+      assert json_response(conn, 200)["results"] == [
+               %{"metrics" => [1], "dimensions" => []}
+             ]
+    end
+
+    test "returns aggregated metrics with shared link auth", %{conn: conn} do
+      site = new_site()
+
+      populate_stats(site, [
+        build(:pageview, user_id: 5, pathname: "/foo", timestamp: ~N[2021-01-01 00:00:00]),
+        build(:pageview, user_id: 5, timestamp: ~N[2021-01-01 00:25:00]),
+        build(:pageview, timestamp: ~N[2021-01-01 00:00:00])
+      ])
+
+      link = insert(:shared_link, site: site)
+
+      conn =
+        post(conn, "/api/stats/#{URI.encode(site.domain)}/query?auth=#{link.slug}", %{
+          "metrics" => ["pageviews"],
+          "date_range" => "all",
+          "filters" => [["is", "event:page", ["/foo"]]]
+        })
+
+      assert json_response(conn, 200)["results"] == [%{"metrics" => [1], "dimensions" => []}]
+    end
+
+    test "returns metrics with shared link auth that is limited to segment", %{conn: conn} do
+      site = new_site()
+
+      populate_stats(site, [
+        build(:pageview, user_id: 5, pathname: "/foo", timestamp: ~N[2021-01-01 00:00:00]),
+        build(:pageview, user_id: 5, timestamp: ~N[2021-01-01 00:25:00]),
+        build(:pageview, timestamp: ~N[2021-01-01 00:00:00])
+      ])
+
+      segment =
+        insert(:segment,
+          site: site,
+          name: "Scandinavia",
+          type: :site,
+          segment_data: %{"filters" => [["is", "event:page", ["/foo"]]]}
+        )
+
+      link = insert(:shared_link, segment_id: segment.id, site: site)
+
+      conn =
+        post(conn, "/api/stats/#{URI.encode(site.domain)}/query?auth=#{link.slug}", %{
+          "metrics" => ["pageviews"],
+          "date_range" => "all",
+          "filters" => [["is", "segment", [segment.id]]]
+        })
+
+      assert json_response(conn, 200)["results"] == [%{"metrics" => [1], "dimensions" => []}]
+    end
+
+    test "errors when expected segment filter not present for shared link auth that is limited to segment",
+         %{conn: conn} do
+      site = new_site()
+
+      segment =
+        insert(:segment,
+          site: site,
+          name: "Scandinavia",
+          type: :site,
+          segment_data: %{"filters" => [["is", "event:page", ["/foo"]]]}
+        )
+
+      link = insert(:shared_link, segment_id: segment.id, site: site)
+
+      conn =
+        post(conn, "/api/stats/#{URI.encode(site.domain)}/query?auth=#{link.slug}", %{
+          "metrics" => ["pageviews"],
+          "date_range" => "all",
+          "filters" => []
+        })
+
+      assert json_response(conn, 400) == %{
+               "error" => "The first filter must be for the segment with id #{segment.id}"
+             }
+    end
+  end
+
+  describe "POST /api/:domain/query" do
+    setup [:create_user, :create_site, :log_in]
+
+    test "rejects when accessing any other site", %{conn: conn, site: site} do
+      conn =
+        post(conn, "/api/stats/any.other.site/query", %{
+          # ignored
+          "site_id" => site.domain,
+          "metrics" => ["pageviews"],
+          "date_range" => "all",
+          "filters" => []
+        })
+
+      assert json_response(conn, 404) == %{
+               "error" => "Site does not exist or user does not have sufficient access."
+             }
+    end
+
+    test "returns aggregated metrics", %{conn: conn, site: site} do
+      populate_stats(site, [
+        build(:pageview, user_id: 5, timestamp: ~N[2021-01-01 00:00:00]),
+        build(:pageview, user_id: 5, timestamp: ~N[2021-01-01 00:25:00]),
+        build(:pageview, timestamp: ~N[2021-01-01 00:00:00])
+      ])
+
+      conn =
+        post(conn, "/api/stats/#{URI.encode(site.domain)}/query?site_id=ignored", %{
+          "metrics" => ["pageviews"],
+          "date_range" => "all",
+          "filters" => []
+        })
+
+      assert json_response(conn, 200)["results"] == [%{"metrics" => [3], "dimensions" => []}]
+    end
+  end
+end