use add_query_arg to determine current page url

includes/admin/class-wc-admin-addons.php

@@ -483,10 +483,12 @@ class WC_Admin_Addons {
 	 * Returns in-app-purchase URL params.
 	 */
 	public static function get_in_app_purchase_url_params() {
-		$back_admin_path = isset( $_SERVER['REQUEST_URI'] ) ? esc_url_raw( wp_unslash( $_SERVER['REQUEST_URI'] ) ) : '';
+		// Get url (from path onward) for the current page,
+		// so WCCOM "back" link returns user to where they were.
+		$back_admin_path = add_query_arg( array() );
 		return array(
 			'in-app-purchase-site'        => site_url(),
-			'in-app-purchase-back'        => $back_admin_path,
+			'in-app-purchase-back'        => esc_url( $back_admin_path ),
 			'in-app-purchase-woo-version' => WC_VERSION,
 		);
 	}