Adversaries may create or modify references in Office document templates to conceal malicious code or force authentication attempts. Microsoft's Office Open XML (OOXML) specification defines an XML-based format for Office documents (.docx, .xlsx, .pptx) to replace older binary formats (.doc, .xls, .ppt). OOXML files are packed together ZIP archives compromised of various XML files, referred to as parts, containing properties that collectively define how a document is rendered.