https://github.com/bitcoin/bitcoin/blob/d72758c3f6c34cd835f5de3efc230964f3b1ea56/src/torcontrol.cpp#L539

If a user is running Tor proxy outside localhost (perhaps on other host inside LAN or in containerised environment) , the automatic creation of onion services ends up creating an onion service listening to hardcored 127.0.0.1 address on the Tor proxy's host instead of the private address of the bitcoind – effectively running an empty onion service listening the Tor proxy's localhost.
{
    std::map<std::string,std::string> mapping;
    size_t ptr=0;
    while (ptr < s.size()) {
        std::string key, value;
        while (ptr < s.size() && s[ptr] != '=' && s[ptr] != ' ') {
            key.push_back(s[ptr]);
            ++ptr;
        }
        if (ptr == s.size()) 
            return std::map<std::string,std::string>();
        if (s[ptr] == ' ') 
            break;
        ++ptr; 
        if (ptr < s.size() && s[ptr] == '"') { 
            ++ptr; 
            bool escape_next = false;
            while (ptr < s.size() && (escape_next || s[ptr] != '"')) {
                
                escape_next = (s[ptr] == '\\' && !escape_next);
                value.push_back(s[ptr]);
                ++ptr;
            }
            if (ptr == s.size()) 
                return std::map<std::string,std::string>();
            ++ptr; 
            /**
             * Unescape value. Per https://spec.torproject.org/control-spec section 2.1.1: