A vulnerability in the REST API of Cisco Firepower Device Manager (FDM) On-Box Software could allow an authenticated, remote attacker to gain read and write access to information that is stored on an affected device. This vulnerability is due to the improper handling of XML External Entity (XXE) entries when parsing certain XML files. An attacker could exploit this vulnerability by sending malicious requests that contain references in XML entities to an affected system. A successful exploit could allow the attacker to retrieve files from the local system, resulting in the disclosure of sensitive information or causing a partial denial of service (DoS) condition on the affected device.