In this script there is no external influence and no transmission of any text data from outside by other users that this code could use, except for the user file that the author creates independently at his own responsibility. The passed identifiers $chan and $1 are known to the script. Therefore, there was no need to specify the additional $unsafe() identifier.
The event react to #channel, which will at best will be changed to an hardcoded channel, but could very well be changed to # to work on all channels, making you vulnerable as $chan alone can be used for exploit
