Expat allows context-dependent attackers to cause a denial of service (crash) or possibly execute arbitrary code via a malformed input document, which triggers a buffer overflow.
https://www.tenable.com/security/tns-2016-20
https://support.apple.com/HT206903
https://source.android.com/security/bulletin/2016-11-01.html
https://security.gentoo.org/glsa/201701-21
https://kc.mcafee.com/corporate/index?page=content&id=SB10365
https://bugzilla.redhat.com/show_bug.cgi?id=1296102
https://bugzilla.mozilla.org/show_bug.cgi?id=1236923
https://access.redhat.com/errata/RHSA-2018:2486
http://www.ubuntu.com/usn/USN-3044-1
http://www.ubuntu.com/usn/USN-2983-1
http://www.securitytracker.com/id/1037705
http://www.securitytracker.com/id/1036415
http://www.securitytracker.com/id/1036348
http://www.securityfocus.com/bid/90729
http://www.oracle.com/technetwork/topics/security/bulletinjul2016-3090568.html
http://www.oracle.com/technetwork/security-advisory/cpujul2018-4258247.html
http://www.openwall.com/lists/oss-security/2016/05/17/12
http://www.mozilla.org/security/announce/2016/mfsa2016-68.html
http://www.debian.org/security/2016/dsa-3582
http://support.eset.com/ca6333/
http://seclists.org/fulldisclosure/2017/Feb/68
http://rhn.redhat.com/errata/RHSA-2016-2824.html
http://packetstormsecurity.com/files/141350/ESET-Endpoint-Antivirus-6-Remote-Code-Execution.html
http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00029.html
http://lists.opensuse.org/opensuse-security-announce/2016-08/msg00004.html
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00010.html
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00007.html
http://lists.opensuse.org/opensuse-security-announce/2016-06/msg00006.html
http://lists.opensuse.org/opensuse-security-announce/2016-05/msg00064.html
http://lists.apple.com/archives/security-announce/2016/Jul/msg00000.html