Simple Execute BASH/ASH Script with URL Code

#This is simple script to execute bash/ash script with URLCODE MultiVariable
#Of course it's vulnerable LOL just for fun :v

#---BEGIN OF SCRIPT ---
IFS=$'&'; parm=$QUERY_STRING; for VAR in $parm; do eval $VAR; done

#var output test
echo $a > /www/a.txt

#---END OF SCRIPT ---

#test with:
#http://192.168.6.1/lop.sh?a=123&b=456&c=ok

#add uhttpd conf /etc/config/uhttpd
...
list interpreter ".sh=/bin/sh"
...