This threat detection rule monitors the creation of files with uncommon extensions within the Microsoft Office startup folders for Word and Excel. The rule aims to identify potentially malicious files that may leverage non-standard extensions and are created at paths that are typically used by legitimate Office applications. It checks specific folders such as `\Microsoft\Word\STARTUP` and `\Microsoft\Excel\XLSTART`, where Office applications usually load files at startup. The rule implements filters to exclude common file extensions related to Microsoft Word and Excel, thus focusing on the creation of files with potentially harmful or uncommon extensions. The detection mechanism ensures that the associated processes correspond to legitimate Office applications, thereby reducing false positives stemming from benign behavior by other Office utilities or from rarer extensions. This rule is marked with a high severity level due to its potential relevance in detecting early stages of file-based malware attacks that could exploit Office applications.