As reported by Github, Openfire should update dom4j:
*Vulnerable versions:* < 2.1.3
*Patched version:* 2.1.3
dom4j before 2.1.3 allows external DTDs and External Entities by default, which might enable XXE attacks. However, there is popular external documentation from OWASP showing how to enable the safe, non-default behavior in any application that uses dom4j.