I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG.  These comments were written primarily for the benefit of the security area directors.  Document editors and WG chairs should treat these comments just like any other last call comments.

The summary of the review is ready.

This document describes the Zstandard data compression mechanism, and registers a MIME media type.

The security considerations section covers all relevant points, I see no security issues with this doc. I did notice a minor typo: page 3, "2.1.1.1.1.  Frame Header Descrptor"

Sorry this review is late, hope it is still helpful.

--Scott