Hack Mikrotik keeps getting a file

All of my routers were hit with this: mikrotik-routeros-remote-vulnerability-exploiting-the-winbox-service

I have cleared them, but I keep getting this in my files:
fetch: file “Update.ashx?key=bdee03097da1df40&action=upload&sncode=796A9E0230273AAF205349B396C1B02F&dynamic=static” downloaded

I delete the file, but about 15 minutes later it reappears.

How can a keep this from happening?

Check on scripts section

Yep, that is what I missed.
Thanks.

Please see this post:

http://forum.mikrotik.com/t/s-o-s-new-vurnelabilty-on-6-42-3-no/120528/1