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.
*
             *   For future-proofing, controller implementors MAY use the following
             *   rules to be compatible with buggy Tor implementations and with
             *   future ones that implement the spec as intended:
             *
             *     Read \n \t \r and \0 ... \377 as C escapes.
             *     Treat a backslash followed by any other character as that character.
             */
            std::string escaped_value;
            for (size_t i = 0; i < value.size(); ++i) {
                if (value[i] == '\\') {
                    
                    
                    
                    
                    ++i;
                    if (value[i] == 'n') {
                        escaped_value.push_back('\n');
                    } else if (value[i] == 't') {
                        escaped_value.push_back('\t');
                    } else if (value[i] == 'r') {
                        escaped_value.push_back('\r');
                    } else if ('0' <= value[i] && value[i] <= '7') {
                        size_t j;
                        
                        
                        
                        for (j = 1; j < 3 && (i+j) < value.size() && '0' <= value[i+j] && value[i+j] <= '7'; ++j) {}