Why do I get the error "Failed to Unzip file 'filename' Exception extracting from zip archive: Damaged or not a zip file." when Cerberus tries to unzip a zip file?

If you are trying to unzip an archive file via the Cerberus Web Client, or using an Event Rule or Scheduled Task, the unzip fails, and you see the error "Unzip file '<zip_name>' to '<folder>' failed: Failed to Unzip file '<zip_name>' Exception extracting from zip archive: Damaged or not a zip file.", it could be because the zip archive you are trying to unzip was created using the 'Deflate64' compression algorithm.

Deflate64 is a compression algorithm, similar to Deflate, but designed to offer potentially better compression at the cost of increased compression time. It's used in some ZIP file implementations, notably by Windows when creating large ZIP archives (generally over 2 GB).

The unzip library currently being used by Cerberus does not support Deflate64 and will not unzip archives created with that compression algorithm. As a workaround, archives intended to be unzipped by Cerberus should not be created using the Deflate64 compression algorithm.

If creating an archive in Windows, do not use the 'Compress to...' option as that uses Deflate64 by default. If possible, we recommend using an arching app like 7Zip to create the archive. 7Zip uses 'Deflate' by default, but you can control the compression algorithm being used when you create the archive. .7z, .tar, and .gz archives do not have this issue.