A XML Exter­nal Enti­ty is a tech­nique where a XML file con­tains a state­ment which leads the XML pars­er to include results from an exter­nal source into the XML file. The benign idea is for exam­ple to replace a string mul­ti­ple times with a pre­de­fined value: <!DOCTYPE data [<!ELEMENT data ANY ><!ENTITY name "Olaf">]><data>...<name>&name;</name>...</data> Impor­tant: data…