Any files placed in this directory will be executed by certspotter, any time a
certificate on the watchlist is found on the CT logs.

Make sure the files have the executable (+x) bit.

certspotter will place several bits of information about the certificate in
question in the environment of the script to be executed. You can consult the
man page certspotter-script(8) for more information on what these variables
are, and how they can be used.
