dcg: Exponential-time command-substitution preprocessing lets a crafted command hang dcg and bypass the guard via hook-timeout fail-open

{
                    "vendor": "Dicklesworthstone",
                    "product": "destructive_command_guard",
                    "versions": [
                        {
                            "version": "< 0.6.6",
                            "status": "affected"
                        }
                    ]
                }