Improper Restriction of XML External Entity Reference
The XLSX2CSV example in Apache POI before 3.14 allows remote attackers to read arbitrary files via a crafted OpenXML document containing an external entity declaration in conjunction with an entity reference, related to an XML External Entity (XXE) issue.
CWE-611 - Improper Restriction of XML External Entity Reference
Listed 4th in the 'OWASP Top Ten', XML External Entities (XXE) vulnerability allows attackers to provide an XML input that contains an external entity. When the XML is parsed, it can cause data extraction and manipulation, execution of commands, denial-of-service attacks, and server-side request forgery.