fix(security): refuse OAuth authorize/consent for users without access (audit L1)

mcp-oauth has no filter for this, so AuthorizeGate runs on
template_redirect before its router and stops the browser endpoints
(authorize, authorize-callback, consent) for logged-in users without
lit_mcp_use with "Dein Benutzer hat keinen Zugriff auf LIT MCP." (403).
Login redirect, token and revoke stay mcp-oauth's.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7

src/Plugin.php

@@ -30,6 +30,7 @@ use LIT\MCP\Integrations\WordPress\Schema\ContentSchema;
 use LIT\MCP\Integrations\WordPress\Schema\RegisteredMetaSource;
 use LIT\MCP\Integrations\WordPress\Schema\SampledMetaSource;
 use LIT\MCP\Integrations\WordPress\WordPressIntegration;
+use LIT\MCP\Server\AuthorizeGate;
 use LIT\MCP\Server\DiscoveryCanonical;
 use LIT\MCP\Server\RequestContext;
 use LIT\MCP\Server\ServerRegistrar;
@@ -60,6 +61,7 @@ final class Plugin
         (new RequestContext())->register();
         (new VisibilityFilter())->register();
         (new DiscoveryCanonical())->register();
+        (new AuthorizeGate())->register();
 
         $limits = new Limits();
         $changeLog = new ChangeLog();

src/Server/AuthorizeGate.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace LIT\MCP\Server;
+
+use LIT\MCP\Access;
+
+/**
+ * Stops mcp-oauth's browser flow for logged-in users without lit_mcp_use (security audit L1).
+ * mcp-oauth only checks is_user_logged_in() and offers no filter, so this runs on
+ * template_redirect before its router (priority 10): without it any customer or subscriber
+ * could complete the consent and get an application password, tokens and sessions, even
+ * though the tools would refuse them. Not logged in, the login redirect stays mcp-oauth's;
+ * token and revoke have no browser session and are left alone.
+ */
+final class AuthorizeGate
+{
+    /** mcp-oauth's query var (WPMedia\MCP\OAuth\Auth\Rewrite::OAUTH_QUERY_VAR). */
+    private const QUERY_VAR = 'mcp_oauth_endpoint';
+
+    /** Endpoints a user reaches in the browser before a connection exists. */
+    private const USER_FACING = ['authorize', 'authorize-callback', 'consent'];
+
+    public function register(): void
+    {
+        add_action('template_redirect', [$this, 'check'], 1);
+    }
+
+    public function check(): void
+    {
+        $endpoint = (string) get_query_var(self::QUERY_VAR, '');
+        if (! in_array($endpoint, self::USER_FACING, true) || ! is_user_logged_in() || Access::currentUserMayUse()) {
+            return;
+        }
+
+        wp_die(
+            esc_html(__('Dein Benutzer hat keinen Zugriff auf LIT MCP.', 'wp-lit-mcp')),
+            esc_html(__('Kein Zugriff', 'wp-lit-mcp')),
+            ['response' => 403]
+        );
+    }
+}