It was part of the broader Microsoft Office for Mac update that included Word, PowerPoint, Outlook, and OneNote.
This was one of the final versions to support macOS Catalina. Microsoft Excel for Mac 16.61
While version 16.61 was largely focused on and bug fixes rather than major new features, it belongs to the version 16 series which introduced: It was part of the broader Microsoft Office
Support for co-authoring and AutoSave for files stored on OneDrive or SharePoint. Microsoft Excel for Mac 16.61
Users typically received this version through Microsoft AutoUpdate . Features and Changes
For a complete history of builds and specific security updates, you can refer to the official Office for Mac update history on Microsoft Learn.