This vulnerability allows remote attackers to execute arbitrary code on affected installations of Foxit PhantomPDF 9.5.0.20723. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The specific flaw exists within the removeField method when processing watermarks within AcroForms. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of the current process. Was ZDI-CAN-8801.
https://www.zerodayinitiative.com/advisories/ZDI-19-631/
https://www.foxitsoftware.com/support/security-bulletins.php