}

		$oth = aioseo()->internalOptions->internal->connect->token;
		if ( empty( $oth ) ) {
			wp_send_json_error( $error );
		}

		// Check if the stored hash matches the salted one that is sent back from the server.
		if ( hash_hmac( 'sha512', $oth, wp_salt() ) !== $hashedOth ) {
			wp_send_json_error( $error );
		}

		// Delete connect token so we don't replay.
		aioseo()->internalOptions->internal->connect->token = null;

		// Verify pro not activated.
		if ( aioseo()->pro ) {
			wp_send_json_success( $success );
		}

		// Check license key.
		$licenseKey = aioseo()->internalOptions->internal->connect->key;
		if ( ! $licenseKey ) {
			wp_send_json_error( esc_html__( 'You are not licensed.', 'all-in-one-seo-pack' ) );
		}

		// Set the license key in a new option so we can get it when Pro is activated.
		aioseo()->internalOptions->internal->validLicenseKey = $licenseKey;

		require_once ABSPATH . 'wp-admin/includes/file.php';
		require_once ABSPATH . 'wp-admin/includes/class-wp-screen.php';
		require_once ABSPATH . 'wp-admin/includes/screen.php';

		// Set the current screen to avoid undefined notices.
		set_current_screen( 'toplevel_page_aioseo' );

		// Prepare variables.
		$url = esc_url_raw(
			add_query_arg(
				[
					'page' => 'aioseo-settings',
				],
				admin_url( 'admin.php' )
			)
		);

		// Verify pro not installed.
		$network = aioseo()->internalOptions->internal->connect->network;
		$active  = activate_plugin( 'all-in-one-seo-pack-pro/all_in_one_seo_pack.php', $url, $network, true );
		if ( ! is_wp_error( $active ) ) {
			aioseo()->internalOptions->internal->connect->reset();

			// Because the regular activation hooks won't run, we need to add capabilities for the installing user so that he doesn't run into an error on the first request.
			aioseo()->activate->addCapabilitiesOnUpgrade();

			wp_send_json_success( $success );
		}

		$creds = request_filesystem_credentials( $url, '', false, false, null );
		// Check for file system permissions.
		if ( false === $creds ) {
			wp_send_json_error( $error );
		}

		$fs = aioseo()->core->fs->noConflict();
		$fs->init( $creds );
		if ( ! $fs->isWpfsValid() ) {
			wp_send_json_error( $error );
		}

		// Do not allow WordPress to search/download translations, as this will break JS output.
		remove_action( 'upgrader_process_complete', [ 'Language_Pack_Upgrader', 'async_upgrade' ], 20 );

		// Create the plugin upgrader with our custom skin.
		$installer = new Utils\PluginUpgraderSilentAjax( new Utils\PluginUpgraderSkin() );

		// Error check.
		if ( ! method_exists( $installer, 'install' ) ) {
			wp_send_json_error( $error );
		}

		$installer->install( $downloadUrl );

		// Flush the cache and return the newly installed plugin basename.
		wp_cache_flush();

		$pluginBasename = $installer->plugin_info();

		if ( ! $pluginBasename ) {
			wp_send_json_error( $error );
		}

		// Activate the plugin silently.
		$activated = activate_plugin( $pluginBasename, '', $network, true );
		if ( is_wp_error( $activated ) ) {
			wp_send_json_error( esc_html__( 'The Pro version installed correctly, but it needs to be activated from the Plugins page inside your WordPress admin.', 'all-in-one-seo-pack' ) );
		}

		aioseo()->internalOptions->internal->connect->reset();

		// Because the regular activation hooks won't run, we need to add capabilities for the installing user so that he doesn't run into an error on the first request.
		aioseo()->activate->addCapabilitiesOnUpgrade();

		wp_send_json_success( $success );
	}
}