This indicates an attack attempt against a Memory Corruption vulnerability in Foxit Reader and PhantomPDF.
The vulnerability is due to an error when the vulnerable software processes specially crafted PDF files with malformed JPXDecode streams. A remote attacker may be able to exploit this to cause a denial of service condition.
Foxit Reader 18.104.22.1684 and earlier on Windows
Foxit Reader 2.0.0.0625 and earlier on Mac OS X
Foxit Reader 1.1.1.0602 and earlier on Linux
Foxit PhantomPDF 22.214.171.1248 and earlier on Windows
Denial of Service: Remote attackers can crash vulnerable systems.
Apply the most recent upgrade or patch from the vendor.