An exploitable arbitrary write vulnerability exists in the open document format parser of the Atlantis Word Processor, version 18.104.22.168, while trying to null-terminate a string. A specially crafted document can allow an attacker to pass an untrusted value as a length to a constructor. This constructor will miscalculate a length and then use it to calculate the position to write a null byte. This can allow an attacker to corrupt memory, which can result in code execution under the context of the application. An attacker must convince a victim to open a specially crafted document in order to trigger this vulnerability.