# 2.4.11 (Not yet released)

## Overview

 * Security: Require ADMIN for `?flush=1` (stop denial of service attacks)
 ([#1692](https://github.com/silverstripe/silverstripe-framework/issues/1692))

## Details

### Security: Require ADMIN for ?flush=1 and ?flush=all

Flushing the various manifests (class, template, config) is performed through a GET
parameter (`flush=1`). Since this action requires more server resources than normal requests,
it can facilitate [denial-of-service attacks](https://en.wikipedia.org/wiki/Denial-of-service_attack).

To prevent this, main.php now checks and only allows the flush parameter in the following cases:

 * The [environment](/topics/environment-management) is in "dev mode"
 * A user is logged in with ADMIN permissions
 * An error occurs during startup

This applies to both `flush=1` and `flush=all`but only through web requests made through main.php - CLI requests,
or any other request that goes through a custom start up script will still process all flush requests as normal.