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Nebula level03 write-up

In Level03 we are said that the program on /flag03 is run by cron every X minutes. If we have a look at the code we can see that it will execute the files in the writable.d directory and then remove them: [email protected]:/home/flag03$ cat #!/bin/sh for i in /home/flag03/writable.d/* ; do (ulimit -t 5; bash -x "$i") rm -f "$i" done Ok, so whatever we put in writable.d will be execute by someone else … but who?