A use after free in the TextBox field Validate action in IReader_ContentProvider can occur for specially crafted PDF files in Foxit Reader SDK (ActiveX) Professional 5.4.0.1031. An attacker can leverage this to gain remote code execution. Relative to CVE-2018-19452, this has a different free location and requires different JavaScript code for exploitation.
https://www.foxitsoftware.com/support/security-bulletins.php