By default, CGI scripts are executed as the "web" user and group, which has almost no privileges on our system. In most cases, this is the best choice, as it controls the damage that a vulnerable script can inflict. However, for some file-management and other applications, it is necessary for a script to run with the full permissions of the user that owns your files (i.e. you, a.k.a. the "me" user ID when viewed from ssh).
To this end, we allow you to set the suid and/or sgid file permission bits on CGI applications. When the suid bit is set, the web server will execute the script using the user id of the owner of the script (provided that the owner of the script is you). When the sgid bit is set, the web server will execute the script using the group id of the group that owns the script. It is safe to use the suid/sgid bits for this purpose; our system does not otherwise honor them.
Please note that there are security implications to running web scripts as your own user ID. If such a script is compromised, you will need to delete your entire site and recreate it from scratch or otherwise manually check every single file because there will be no other way to ensure that other files have not been subtly changed. For this reason, we strongly discourage the indiscriminate use of this feature as a substitute for properly setting up file permissions.