The XML parsers in iText before 5.5.12 and 7.x before 7.0.3 do not disable external entities, which might allow remote attackers to conduct XML external entity (XXE) attacks via a crafted PDF.
https://www.oracle.com/security-alerts/cpuoct2020.html
https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbhf03902en_us
http://www.securityfocus.com/archive/1/541483/100/0/threaded