A use-after-free vulnerability exists in the JavaScript engine of Foxit Software's Foxit PDF Reader version 9.1.0.5096. A use-after-free condition can occur when accessing the Keywords property of the this.info object. An attacker needs to trick the user to open the malicious file to trigger this vulnerability. If the browser plugin extension is enabled, visiting a malicious site can also trigger the vulnerability.
https://www.foxitsoftware.com/support/security-bulletins.php
https://talosintelligence.com/vulnerability_reports/TALOS-2018-0628