Steps:
EnableRemoteCommands=1
DenyKey=system.run[*]
Execute global script through frontend

-Unsupported item key.
-Cannot execute script

Expected:
Should be clear that it is forbidden to use this key due to DenyKey setting.

For example:
Item key is not allowed

Another issue:
./bin/zabbix_get -s 127.0.0.1 -k "system.run[echo 2]"

Result:
ZBX_NOTSUPPORTED: Unsupported item key.

Make you think that something is wrong with the key but it is not !