Security researchers released a wicked variant of Clippy, the recently resurfaced assistant in Microsoft Office that we all loved so much to hate, that makes it more difficult to detect a malicious macro in documents. The tool modifies Office documents at file format level to spew out malicious versions that get by the static analysis of antivirus engines and even utilities for manual inspection of macro scripts. Researchers at Dutch security testing company Outflank developed Evil Clippy for professionals running red team attacks against a client organization.
Source: https://www.bleepingcomputer.com/news/security/evil-clippy-makes-malicious-office-docs-that-dodge-detection/