Capsicum is a lightweight OS capability and sandbox framework provided by FreeBSD. When built with Capsicum support - which is the default under FreeBSD - Irssi can enter a Capsicum capability mode (a sandbox), greatly limiting possible consequences of a potential security hole in Irssi or the libraries it depends on. To make Irssi enter capability mode on startup, add capsicum = "yes"; awaylog_file = "~/irclogs/away.log"; to your ~/.irssi/config and restart the client. Alternatively you can enter it "by hand", using the "/capsicum enter" command. From the security point of view it's strongly preferable to use the former method, to avoid establishing connections without the sandbox protection; the "/capsicum" command is only intended for experimentation, and in cases where you need to do something that's not possible in capability mode - run scripts, for example - before continuing. There is no way to leave the capability mode, apart from exiting Irssi. When running in capability mode, there are certain restrictions - Irssi won't be able to access any files outside the directory pointed to by capsicum_irclogs_path (which defaults to ~/irclogs/). If you change the path when already in capability mode it won't be effective until you restart Irssi. Capability mode also makes it impossible to use the "/save" command. Currently there is no way to use custom SSL certificates. As a workaround you can establish connections and enter the capability mode afterwards using the "/capsicum enter" command.